You searched for +publisher:"Virginia Tech" +contributor:("Stutzman, Warren L.").
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Virginia Tech
1.
O'Donnell, Alan Larkin.
New Approach to finding Active Element Patterns for Large Arrays.
Degree: MS, Electrical Engineering, 2013, Virginia Tech
URL: http://hdl.handle.net/10919/23221 
► In this study a new approach to active-element pattern analysis, for large phased array antennas, was created using Floquet\'s theorem. The classic approach to finding…
(more)
▼ In this study a new approach to active-element pattern analysis, for large phased array antennas, was created using Floquet\'s theorem. The classic approach to finding active-element patterns uses a full array simulation that can become slow and produce patterns that are specific to certain elements in the array, though basically identical away from the array edge. Instead of producing specific active-element patterns an average active-element pattern could be created and then applied that to the array. The average active-element pattern can be used for every element in the array with a small margin of error. Using Floquet\'s theorem reduces any differences between elements in the array and gives the most accurate active-element pattern within a reasonable time constraint. Floquet average active-element patterns are computed by using an infinite array and a summation is done for the far-field radiation values of a finite array based on the number of elements using typical pattern multiplication techniques. Therefore, accuracy of the Floquet element approach is excellent for arrays on the size of hundreds to thousands of elements. An active-element pattern is determined by scanning the array and taking the far-field radiation value at each beam scan-angle. Each beam scan-angle value is a summation of the element radiation patterns in that specific direction. These beam scan-angle values are then reduced by the number of elements in the array to form a radiation pattern. This radiation pattern is the average active-element pattern.
Advisors/Committee Members: Davis, William A. (committeechair), Stutzman, Warren L. (committee member), Manteghi, Majid (committee member).
Subjects/Keywords: Acive-element patterns; large arrays; Floquet
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APA (6th Edition):
O'Donnell, A. L. (2013). New Approach to finding Active Element Patterns for Large Arrays. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/23221
Chicago Manual of Style (16th Edition):
O'Donnell, Alan Larkin. “New Approach to finding Active Element Patterns for Large Arrays.” 2013. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/23221.
MLA Handbook (7th Edition):
O'Donnell, Alan Larkin. “New Approach to finding Active Element Patterns for Large Arrays.” 2013. Web. 22 Jan 2021.
Vancouver:
O'Donnell AL. New Approach to finding Active Element Patterns for Large Arrays. [Internet] [Masters thesis]. Virginia Tech; 2013. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/23221.
Council of Science Editors:
O'Donnell AL. New Approach to finding Active Element Patterns for Large Arrays. [Masters Thesis]. Virginia Tech; 2013. Available from: http://hdl.handle.net/10919/23221
Virginia Tech
2.
Yang, Taeyoung.
Fundamental Limits on Antenna Size for Frequency and Time Domain Applications.
Degree: PhD, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/39334
► As ubiquitous wireless communication becomes part of life, the demand on antenna miniaturization and interference reduction becomes more extreme. However, antenna size and performance are…
(more)
▼ As ubiquitous wireless communication becomes part of life, the demand on antenna miniaturization and interference reduction becomes more extreme. However, antenna size and performance are limited by radiation physics, not technology.
In order to understand antenna radiation and energy storage mechanisms, classical and alternative viewpoints of radiation are discussed. Unlike the common sense of classical antenna radiation, it is shown that the entire antenna fields contribute to both radiation and energy storage with varying total energy velocity during the radiation process. These observations were obtained through investigating impedance, power, the Poynting vector, and energy velocity of a radiating antenna.
Antenna transfer functions were investigated to understand the real-world challenges in antenna design and overall performance. An extended model, using both the singularity expansion method and spherical mode decomposition, is introduced to analyze the characteristics of various antenna types including resonant, frequency-independent, and ultra-wideband antennas. It is shown that the extended model is useful to understand real-world antennas.
Observations from antenna radiation physics and transfer function modeling lead to both corrections and extension of the classical fundamental-limit theory on antenna size. Both field and circuit viewpoints of the corrected limit theory are presented. The corrected theory is extended for multi-mode excitation cases and also for ultra-wideband and frequency-independent antennas.
Further investigation on the fundamental-limit theory provides new innovations, including a low-Q antenna design approach that reduces antenna interference issues and a generalized approach for designing an antenna close to the theoretical-size limit. Design examples applying these new approaches with simulations and measurements are presented.
The extended limit theory and developed antenna design approaches will find many applications to optimize compact antenna solutions with reduced near-field interactions.
Advisors/Committee Members: Beattie, Christopher A. (committee member), Reed, Jeffrey Hugh (committee member), Ellingson, Steven W. (committee member), Davis, William A. (committeecochair), Stutzman, Warren L. (committeecochair).
Subjects/Keywords: Antenna Radiation Physics; Near-Field Interaction; Ultra-Wideband Antenna; Antenna Transfer Function; Fundamental-Limit Theory on Antenna
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APA (6th Edition):
Yang, T. (2012). Fundamental Limits on Antenna Size for Frequency and Time Domain Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/39334
Chicago Manual of Style (16th Edition):
Yang, Taeyoung. “Fundamental Limits on Antenna Size for Frequency and Time Domain Applications.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/39334.
MLA Handbook (7th Edition):
Yang, Taeyoung. “Fundamental Limits on Antenna Size for Frequency and Time Domain Applications.” 2012. Web. 22 Jan 2021.
Vancouver:
Yang T. Fundamental Limits on Antenna Size for Frequency and Time Domain Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/39334.
Council of Science Editors:
Yang T. Fundamental Limits on Antenna Size for Frequency and Time Domain Applications. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/39334
Virginia Tech
3.
Hearn, Christian Windsor.
Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments.
Degree: PhD, Electrical Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/49554
► Bandwidth enhancement of low-profile omnidirectional, electrically-small antennas has evolved from the design and construction of AM transmitter towers eighty years ago to current market demand…
(more)
▼ Bandwidth enhancement of low-profile omnidirectional, electrically-small antennas has evolved from the design and construction of AM transmitter towers eighty years ago to current market demand for battery-powered personal communication devices. Electrically-small antenna theory developed with well-known approximations for characterizing radiation properties of antenna structures that are fractions of the radiansphere. Current state-of-the-art wideband small antennas near kaH1 have achieved multiple-octave impedance bandwidths when utilizing volume-efficient designs. Significant advances in both the power and miniaturization of microelectronics have created a second possible approach to enhance bandwidth. Frequency agility, via switch tuning of reconfigurable structures, offers the possibility of the direct integration of high-speed electronics to the antenna structure. The potential result would provide a means to translate a narrow instantaneous bandwidth across a wider operating bandwidth. One objective of the research was to create a direct comparison of the passive- multi-resonant and active-reconfigurable approaches to enhance bandwidth. Typically, volume-efficient, wideband antennas are unattractive candidates for low-profile applications and conversely, active electronics integrated directly antenna elements continue to introduce problematic loss mechanisms at the proof-of-concept level. The dissertation presents an analysis method for wide bandwidth self-resonant antennas that exist in the 0.5dkad1.0 range. The combined approach utilizes the quality factor extracted directly from impedance response data in addition to near-and-far field modal analyses. Examples from several classes of antennas investigated are presented with practical boundary conditions. The resultant radiation properties of these antenna-finite ground plane systems are characterized by an appreciable percentage of radiated power outside the lowest-order mode. Volume-efficient structures and non-omnidirectional radiation characteristics are generally not viable for portable devices. Several examples of passive structures, representing different antenna classes are investigated. A PIN diode, switch-tuned low-profile antenna prototype was also developed for the comparison which demonstrated excessive loss in the physical prototype. Lastly, a passive, low-profile multi-resonant antenna element with monopole radiation is introduced. The structure is an extension of the planar inverted-F antenna with the addition of a capacitance-coupled parasitic to enhance reliable operation in unknown environments.
Advisors/Committee Members: Davis, William A. (committeechair), Kohler, Werner E. (committee member), Stutzman, Warren L. (committee member), Pratt, Timothy J. (committee member), Manteghi, Majid (committee member).
Subjects/Keywords: Multi-resonant small antenna; spherical mode decomposition
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APA (6th Edition):
Hearn, C. W. (2012). Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/49554
Chicago Manual of Style (16th Edition):
Hearn, Christian Windsor. “Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/49554.
MLA Handbook (7th Edition):
Hearn, Christian Windsor. “Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments.” 2012. Web. 22 Jan 2021.
Vancouver:
Hearn CW. Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/49554.
Council of Science Editors:
Hearn CW. Electrically-Small Antenna Performance Enhancement for Near-Field Detuning Environments. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/49554
Virginia Tech
4.
Hong, Sun.
Resonance-Based Techniques for Microwave Breast Cancer Applications.
Degree: PhD, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/29096
► It is well known that a finite-size scatterer has a set of natural resonances, which are uniquely determined by the physical properties of the scatterer.…
(more)
▼ It is well known that a finite-size scatterer has a set of natural resonances, which are uniquely determined by the physical properties of the scatterer. This is also the case for a breast tumor which can be regarded as a dielectric scatterer. Since the scatterer is naturally "tuned" at the resonances, it is expected that an increased electromagnetic coupling would take place at the resonance frequencies compared to other frequencies. For a breast tumor, this would mean a higher power absorption, indicating a faster temperature increase resulting in more efficient hyperthermia.
In this dissertation, an adaptive microwave concept is demonstrated for breast cancer applications. The general approach is to detect and identify the tumor-specific resonance, determine the electrical location of the tumor, and apply the focused microwave hyperthermia using the identified resonance and the electrical location. The natural resonances vary depending on the tumor size, shape, and breast tissue configuration. Therefore, an adaptive tuning of the microwave source to tumor-specific resonance frequencies could improve the overall efficiency of hyperthermia treatment by allowing for a faster and more effective heating to achieve a desired therapeutic temperature level.
Applying the singularity expansion method (SEM), both the resonances and the electrical location can be obtained from the poles and residues, respectively. This SEM-based approach is computationally inexpensive and can easily be implemented as a combination processing into emerging UWB microwave systems. Alternatively, a relatively simple microwave system based on this concept can potentially be used in conjunction with existing mammography.
Advisors/Committee Members: Davis, William A. (committeechair), Stutzman, Warren L. (committee member), Safaai-Jazi, Ahmad (committee member), Pratt, Timothy J. (committee member), Adjerid, Slimane (committee member).
Subjects/Keywords: natural resonance; breast cancer; microwave hyperthermia; residue; singularity expansion method; pole; ground penetrating radar
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APA (6th Edition):
Hong, S. (2012). Resonance-Based Techniques for Microwave Breast Cancer Applications. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/29096
Chicago Manual of Style (16th Edition):
Hong, Sun. “Resonance-Based Techniques for Microwave Breast Cancer Applications.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/29096.
MLA Handbook (7th Edition):
Hong, Sun. “Resonance-Based Techniques for Microwave Breast Cancer Applications.” 2012. Web. 22 Jan 2021.
Vancouver:
Hong S. Resonance-Based Techniques for Microwave Breast Cancer Applications. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/29096.
Council of Science Editors:
Hong S. Resonance-Based Techniques for Microwave Breast Cancer Applications. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/29096
Virginia Tech
5.
Alsawaha, Hamad Waled.
Synthesis of Ultra-Wideband Array Antennas.
Degree: PhD, Electrical Engineering, 2014, Virginia Tech
URL: http://hdl.handle.net/10919/54553
► Acquisition of ultra-wideband signals by means of array antennas requires essentially frequency-independent radiation characteristics over the entire bandwidth of the signal in order to avoid…
(more)
▼ Acquisition of ultra-wideband signals by means of array antennas requires essentially frequency-independent radiation characteristics over the entire bandwidth of the signal in order to avoid distortions. Factors contributing to bandwidth limitation of arrays include array factor, radiation characteristics of the array element, and inter-element mutual coupling. Strictly speaking, distortion-free transmission or reception of ultra-wideband signals can be maintained if the magnitude of the radiated field of the array remains constant while its phase varies linearly with frequency over the bandwidth of interest. The existing wideband-array synthesis methods do not account for all factors affecting the array bandwidth and are often limited to considering the array factor and not the total field of the array in the synthesis process.
The goal of this study is to present an ultra-wideband array synthesis technique taking into account all frequency-dependent properties, including array total pattern, phase of the total radiated field, element field, element input impedance, and inter-element mutual coupling. The proposed array synthesis technique is based on the utilization of frequency-adaptive element excitations in conjunction with expressing the total radiated field of the array as a complex Fourier series. Using the proposed method, element excitation currents required for achieving a desired radiation pattern, while compensating for frequency variations of the element radiation characteristics and the inter-element mutual coupling, are calculated.
An important consideration in the proposed ultra-wideband array design is that the "phase bandwidth", defined as the frequency range over which the phase of the total radiated field of the array varies linearly with frequency, is taken into account as a design requirement in the synthesis process. Design examples of linear arrays with desired radiation patterns that are expected to remain unchanged over the bandwidth of interest are presented and simulated. Two example arrays, one with a wire dipole as its element and another using an elliptically-shaped disc dipole as the element are studied. Simulation results for far-field patterns, magnitude and phase characteristics, and other performance criteria such as side-lobe level and scanning range are presented.
Synthesis of two-dimensional planar arrays is carried out by employing the formulations developed for linear arrays but generalized to accommodate the geometry of planar rectangular arrays. As example designs, planar arrays with wire dipoles and elliptical-shaped disc dipoles are studied. The simulation results indicate that synthesis of ultra-wideband arrays can be accomplished successfully using the technique presented in this work. The proposed technique is robust and comprehensive, nonetheless it is understood that the achieved performance of a synthesized array and how closely the desired performance is met also depends on some of the choices the array designer makes and other constraints, such as number of…
Advisors/Committee Members: Safaai-Jazi, Ahmad (committeechair), Brown, Gary S. (committee member), Pratt, Timothy J. (committee member), Davis, William A. (committee member), Stutzman, Warren L. (committee member), Kohler, Werner E. (committee member).
Subjects/Keywords: antenna arrays; array synthesis; ultra-wideband antenna arrays
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APA (6th Edition):
Alsawaha, H. W. (2014). Synthesis of Ultra-Wideband Array Antennas. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/54553
Chicago Manual of Style (16th Edition):
Alsawaha, Hamad Waled. “Synthesis of Ultra-Wideband Array Antennas.” 2014. Doctoral Dissertation, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/54553.
MLA Handbook (7th Edition):
Alsawaha, Hamad Waled. “Synthesis of Ultra-Wideband Array Antennas.” 2014. Web. 22 Jan 2021.
Vancouver:
Alsawaha HW. Synthesis of Ultra-Wideband Array Antennas. [Internet] [Doctoral dissertation]. Virginia Tech; 2014. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/54553.
Council of Science Editors:
Alsawaha HW. Synthesis of Ultra-Wideband Array Antennas. [Doctoral Dissertation]. Virginia Tech; 2014. Available from: http://hdl.handle.net/10919/54553
Virginia Tech
6.
Vasavada, Yash M.
An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems.
Degree: PhD, Electrical and Computer Engineering, 2012, Virginia Tech
URL: http://hdl.handle.net/10919/28192
► This dissertation proposes an iterative confidence passing (ICP) approach for parameter estimation. The dissertation describes three different algorithms that follow from this ICP approach. These…
(more)
▼ This dissertation proposes an iterative confidence passing (ICP) approach for parameter estimation. The dissertation describes three different algorithms that follow from this ICP approach. These three variations of the ICP approach are applied to (a) macrodiversity and user cooperation diversity reception problems, (b) the co-operative multipoint MIMO reception problem (pertinent to the LTE Advanced system scenarios), and (c) the satellite beamforming problem. The first two of these three applications are some of the significant open DSP research problems that are currently being actively pursued in academia and industry. This dissertation demonstrates a significant performance improvement that the proposed ICP approach delivers compared to the existing known techniques.
The proposed ICP approach jointly estimates (and, thereby, separates) two sets of unknown parameters from the receiver measurements. For applications (a) and (b) mentioned above, one set of unknowns is comprised of the discrete-valued information-bearing transmitted symbols in a multi-channel communication system, and the other set of unknown parameters is formed by the coefficients of a Rayleigh or Rician fading channel. Application (a) is for interference-free, cooperative or macro, transmit or receive, diversity scenarios. Application (b) is for MIMO systems with interference-rich reception. Finally, application (c) is for an interference-free spacecraft array calibration system model in which both the sets of unknowns are complex continuous valued variables whose magnitude follows the Rician distribution.
The algorithm described here is the outcome of an investigation for solving a difficult channel estimation problem. The difficulty of the estimation problem arises because (i) the channel of interest is intermittently observed, and (ii) the partially observed information is not directly of the channel of interest; it has dependency on another unknown and uncorrelated set of complex-valued random variables.
The proposed ICP algorithmic approach for solving the above estimation problems is based on an iterative application of the Weighted Least Squares (WLS) method. The main novelty of the proposed algorithm is a back and forth exchange of the confidence or the belief values in the WLS estimates of the unknown parameters during the algorithm iterations. The confidence values of the previously obtained estimates are used to derive the estimation weights at the next iteration, which generates an improved estimate with a greater confidence. This method of iterative confidence (or belief) passing causes a bootstrapping convergence to the parameter estimates.
Besides the ICP approach, several alternatives are considered to solve the above problems (a, b and c). Results of the performance simulation of the alternative methods show that the ICP algorithm outperforms all the other candidate approaches. Performance benefit is significant when the measurements (and the initial seed estimates) have non-uniform quality, e.g., when many of the…
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Beex, A. A. Louis (committee member), Tranter, William H. (committee member), Stutzman, Warren L. (committee member), Rossi, John F. (committee member).
Subjects/Keywords: Probabilistic Inference; Beamforming; Optimum Diversity Combining; MMSE; Least Squares; Bayesian Belief Theory; Iterative Estimation
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APA (6th Edition):
Vasavada, Y. M. (2012). An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/28192
Chicago Manual of Style (16th Edition):
Vasavada, Yash M. “An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems.” 2012. Doctoral Dissertation, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/28192.
MLA Handbook (7th Edition):
Vasavada, Yash M. “An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems.” 2012. Web. 22 Jan 2021.
Vancouver:
Vasavada YM. An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/28192.
Council of Science Editors:
Vasavada YM. An Iterative Confidence Passing Approach for Parameter Estimation and Its Applications to MIMO Systems. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/28192
Virginia Tech
7.
Werntz, Paul C.
Analysis, design, and fabrication of Archimedean spiral antennas.
Degree: MS, Electrical Engineering, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/45941
► The uses for wideband antennas include wideband measurement systems, spread spectrum communications systems, feeds for reflectors and elements in wideband arrays. Here, wideband antennas…
(more)
▼ The uses for wideband antennas include wideband measurement systems, spread
spectrum communications systems, feeds for reflectors and elements in wideband arrays.
Here, wideband antennas are discussed and Archimedean spiral antennas are found to
be appropriate elements for use in a new type of wideband array referred to as the
wideband switched array. The design of an Archimedean spiral and a necessary
wideband balun transformer feed structure are presented. To aid in the design, the
Electromagnetic Surface Patch Code (ESP) developed by Ohio State University is used.
The spiral and feed structure are constructed and measured results are compared to
predictions obtained by ESP.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Brown, Gary S. (committee member), Davis, William A. (committee member).
Subjects/Keywords: Spiral antennas; LD5655.V855 1988.W474
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APA (6th Edition):
Werntz, P. C. (1988). Analysis, design, and fabrication of Archimedean spiral antennas. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/45941
Chicago Manual of Style (16th Edition):
Werntz, Paul C. “Analysis, design, and fabrication of Archimedean spiral antennas.” 1988. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/45941.
MLA Handbook (7th Edition):
Werntz, Paul C. “Analysis, design, and fabrication of Archimedean spiral antennas.” 1988. Web. 22 Jan 2021.
Vancouver:
Werntz PC. Analysis, design, and fabrication of Archimedean spiral antennas. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/45941.
Council of Science Editors:
Werntz PC. Analysis, design, and fabrication of Archimedean spiral antennas. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/45941
Virginia Tech
8.
Hearn, Christian W.
Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications.
Degree: MS, Electrical Engineering, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/35286
► Virginia Tech, Utah State University, and the University of Washington were teamed to form the Ionospheric Observation Nanosat Formation to investigate formation-flying requirements for multiple…
(more)
▼ Virginia Tech, Utah State University, and the University of Washington were teamed to form the Ionospheric Observation Nanosat Formation to investigate formation-flying requirements for multiple spacecraft missions. A communication subsystem for the mission will comprise an uplink, downlink and a satellite-to-satellite crosslink.
A linearly polarized resonant loop antenna mounted above the bottom surface of the spacecraft was selected for a possible satellite uplink receive antenna. The resonant loop was chosen to satisfy the physical requirements of the spacecraft whild still achieving efficient operation for a UHF signal.
A full-scale prototype was fabricated to measure frequency dependent characteristics of the antenna. A gamma match and a quarter-wave sleeve balun transformer were integrated to the system to minimize the power reflected at the antenna input and to isolate the antenna from the feed line.
The uplink antenna demonstrated sufficient performance; however, the final bandwidth of less than one percent will require additional tuning as other subsystems are integrated into the final flight-ready prototype.
Advisors/Committee Members: Scales, Wayne A. (committeechair), Davis, William A. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: uplink antenna; nanosatellite; UHF
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APA (6th Edition):
Hearn, C. W. (2001). Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35286
Chicago Manual of Style (16th Edition):
Hearn, Christian W. “Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications.” 2001. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/35286.
MLA Handbook (7th Edition):
Hearn, Christian W. “Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications.” 2001. Web. 22 Jan 2021.
Vancouver:
Hearn CW. Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/35286.
Council of Science Editors:
Hearn CW. Electrical Design and Testing of an Uplink Antenna for Nanosatellite Applications. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/35286
Virginia Tech
9.
Nicoloso, Steven P.
An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments.
Degree: MS, Electrical and Computer Engineering, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/35869
► The challenge of carrier recovery for digitally phase modulated, suppressed-carrier signals has been the target of much attention in mobile radio system design for many…
(more)
▼ The challenge of carrier recovery for digitally phase modulated, suppressed-carrier signals has been the target of much attention in mobile radio system design for many years. Code division multiple access (CDMA) cellular systems are now being deployed in mobile environments, and the performance of carrier recovery for CDMA is much less well understood. CDMA systems typically utilize lower bit energies, relying instead upon coding gain for reliable performance. As an additional challenge, the multiple access interference (MAI) inherent to direct-sequence spread-spectrum (DSSS) signalling further hampers many carrier recovery techniques.
This thesis first surveys general carrier recovery strategies, conventional as well as new, and then applies them to the particular task of recovering a suppressed carrier in mobile CDMA systems. First some of the theory surrounding conventional, closed-loop, carrier recovery techniques and several newer open-loop estimation structures, based on the maximum likelihood (ML) principle is presented. A novel decision-feedback ML phase estimator is proposed. The statistical behavior of this new structure as well as the related squaring estimator are examined and are shown to be equivalent to the stochastic performance of classical closed-loop techniques.
Candidate receivers based upon closed- and open-loop carrier recovery structures are proposed and then examined via simulation. Both forward and reverse cellular links are examined under a variety of both of single-path and multipath conditions. The notion of exploiting cyclostationary MAI in CDMA systems by applying adaptive receiver techniques is also examined, especially as this scheme relies to some extent upon coherent carrier recovery for its promising performance enhancements. This work concludes with recommendations of the best carrier recovery strategies for the variety of environments examined and suggestions for future research are made.
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Woerner, Brian D. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: none
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APA (6th Edition):
Nicoloso, S. P. (1997). An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35869
Chicago Manual of Style (16th Edition):
Nicoloso, Steven P. “An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments.” 1997. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/35869.
MLA Handbook (7th Edition):
Nicoloso, Steven P. “An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments.” 1997. Web. 22 Jan 2021.
Vancouver:
Nicoloso SP. An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments. [Internet] [Masters thesis]. Virginia Tech; 1997. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/35869.
Council of Science Editors:
Nicoloso SP. An Investigation of Carrier Recovery Techniques for PSK Modulated Signals in CDMA and Mulipath Mobile Environments. [Masters Thesis]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/35869
Virginia Tech
10.
Allnutt, Richard Mallory.
Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech.
Degree: MS, Electrical Engineering, 1991, Virginia Tech
URL: http://hdl.handle.net/10919/44203
► This paper discusses the total power radiometers in the propagation experiment at Virginia Tech using the OLYMPUS communications satellite. The experiment is set up…
(more)
▼ This paper discusses the total power radiometers in the propagation experiment at
Virginia Tech using the OLYMPUS communications satellite. The experiment is set up to
measure the received signal strength of beacons at 12.502, 19.770 and 29.656 GHz on board the
OL YMPUS satellite in order to gather space-earth propagation statistics for a period of one
year. The radiometers are used to set the clear sky reference levels for the beacon receivers.
The paper begins with an overview of radio signal attenuation mechanisms, and a general
discussion of radiometry. A description of the OLYMPUS radiometers follows, with sections on
calibration techniques and the methods required to convert radiometer data into derived path
attenuation for use in setting the clear air reference levels for the beacon receivers.
Several novel techniques were used in the
Virginia Tech radiometers including the use of
voltage to frequency converters for integration purposes, and reference load calibration using a
waveguide switch to swap the radiometer input from the antenna to a waveguide load of known
and stable temperature. The penultimate chapter contains data recorded in the course of the
experiment which was selected at random from the month of January 1991. The data is
compared to corresponding free space beacon attenuation data and shows conclusively that the
total power radiometer can produce highly accurate and stable attenuation measurements for
extended periods of time.
Advisors/Committee Members: Pratt, Timothy J. (committeechair), Stutzman, Warren L. (committee member), Bostian, Charles W. (committee member).
Subjects/Keywords: Artificial satellites in telecommunication.; LD5655.V855 1991.A556
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APA (6th Edition):
Allnutt, R. M. (1991). Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44203
Chicago Manual of Style (16th Edition):
Allnutt, Richard Mallory. “Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech.” 1991. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/44203.
MLA Handbook (7th Edition):
Allnutt, Richard Mallory. “Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech.” 1991. Web. 22 Jan 2021.
Vancouver:
Allnutt RM. Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech. [Internet] [Masters thesis]. Virginia Tech; 1991. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/44203.
Council of Science Editors:
Allnutt RM. Total power radiometers at 12, 20 and 30 GHz used in the OLYMPUS experiment at Virginia Tech. [Masters Thesis]. Virginia Tech; 1991. Available from: http://hdl.handle.net/10919/44203
Virginia Tech
11.
Ajaz, Haroon.
Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons.
Degree: MS, Electrical Engineering, 1993, Virginia Tech
URL: http://hdl.handle.net/10919/46088
► Fade and inter-fade duration data obtained from the three beacons at 12, 20, and 30 GHz aboard the OLYMPUS satellite were analyzed. The different…
(more)
▼ Fade and inter-fade duration data obtained from the three beacons at 12, 20, and
30 GHz aboard the OLYMPUS satellite were analyzed.
The different types of signal impairments and their causes were highlighted and a
literature survey conducted. Twelve months of fade and inter-fade data were analyzed and
the results of these statistics are presented in the form of tables and figures. The analysis
was done on both the monthly and annual data. These tables and figures show that at the
higher fade levels, the number of fade events and the fade time is smaller than at the lower
thresholds. For the same fade level the number of fade events and the fade time goes down
as the fade duration which it exceeds is increased. Inter-fade durations also showed similar results.
The fades exhibited seasonal dependencies. The number of fades (and consequently
the fade time) were much higher for the months of May through August and for the
months of March and December. The other months showed very little fade activity.
A model was also constructed that can predict the fade time as a function of
frequency, attenuation level, and fade duration interval. The predicted fade times agree
well with the measured fade duration data. An alternate simplified version of the model is
also presented.
Advisors/Committee Members: Safaai-Jazi, Ahmad (committeechair), Stutzman, Warren L. (committee member), Pratt, Timothy J. (committee member).
Subjects/Keywords: Artificial satellites in telecommunication.; LD5655.V855 1993.A429
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APA (6th Edition):
Ajaz, H. (1993). Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/46088
Chicago Manual of Style (16th Edition):
Ajaz, Haroon. “Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons.” 1993. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/46088.
MLA Handbook (7th Edition):
Ajaz, Haroon. “Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons.” 1993. Web. 22 Jan 2021.
Vancouver:
Ajaz H. Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons. [Internet] [Masters thesis]. Virginia Tech; 1993. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/46088.
Council of Science Editors:
Ajaz H. Study of fade and inter-fade durations in Ku- and Ka- band frequencies using OLYMPUS satellite beacons. [Masters Thesis]. Virginia Tech; 1993. Available from: http://hdl.handle.net/10919/46088
Virginia Tech
12.
Mousselon, Laure.
Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems.
Degree: MS, Electrical and Computer Engineering, 2003, Virginia Tech
URL: http://hdl.handle.net/10919/10155
► The performance of a mobile satellite communications link is conditioned by the characteristics of the propagation path between a satellite and mobile users. The most…
(more)
▼ The performance of a mobile satellite communications link is conditioned by the characteristics of the propagation path between a satellite and mobile users. The most important propagation effect in land mobile satellite system is roadside attenuation of the signals due to vegetation or urban structures. System designers should have the most reliable information about the statistics of the propagation channel to build reliable systems that can compensate for bad propagation conditions.
In 1998, the
Virginia Tech Antenna Group developed a simulator, PROSIM, to simulate a propagation channel in the case of roadside tree attenuation in land mobile satellite systems. This thesis describes some improvements to PROSIM, and the adaptation and validation of PROSIM for Digital Audio Radio Satellite systems operating at S-band frequencies. The performance of the simulator for S-band frequencies was evaluated through a measurement campaign conducted with the XM Radio signals at 2.33 GHz in various propagation environments. Finally, additional results on dual satellite systems and fade correlation are described.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Pratt, Timothy J. (committee member), Davis, William A. (committee member).
Subjects/Keywords: Cumulative Fade Distribution; Measurements; Lognormal; LMSS; S-band; Propagation Model; DARS; Shadowing; Propagation Simulator; Average Fade Duration; Level Crossing Rate; Rayleigh; Ricean; Dual Satellites
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APA (6th Edition):
Mousselon, L. (2003). Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/10155
Chicago Manual of Style (16th Edition):
Mousselon, Laure. “Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems.” 2003. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/10155.
MLA Handbook (7th Edition):
Mousselon, Laure. “Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems.” 2003. Web. 22 Jan 2021.
Vancouver:
Mousselon L. Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems. [Internet] [Masters thesis]. Virginia Tech; 2003. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/10155.
Council of Science Editors:
Mousselon L. Radio Wave Propagation Measurements and Modeling for Land Mobile Satellite Systems. [Masters Thesis]. Virginia Tech; 2003. Available from: http://hdl.handle.net/10919/10155
Virginia Tech
13.
Gobien, Andrew Timothy III.
Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios.
Degree: MS, Electrical Engineering, 1997, Virginia Tech
URL: http://hdl.handle.net/10919/36959
► Antennas in hand-held radios must be compact and unobtrusive. Electrically small and low-profile antennas experience high input reactance, low input resistance, and low radiation efficiency.Further…
(more)
▼ Antennas in hand-held radios must be compact and unobtrusive. Electrically small and low-profile antennas experience high input reactance, low input resistance, and low radiation efficiency.Further degradation of radiation efficiency occurs in hand-held radios due to size-reduced ground planes, losses within the plastic device casing, and losses due to coupling with the tissue of the user. These factors may also affect the radiation pattern of the antenna.
This discussion reports on antenna designs that are well suited for hand-held radios. The design issues are covered for electrically small antennas and the hand-held environment. A review of Microstrip Antenna (MSA) theory, and the theory of the Inverted-
L Antenna (ILA), and variations on the ILA including the Inverted-F Antenna (IFA), Planar Inverted-F Antenna (PIFA), and Dual Inverted-F Antenna (DIFA) is included. Two specific antenna designs are presented: the DIFA and the Proximity-Coupled Rectangular Patch MSA. The radiation patterns and input impedance of the DIFA are calculated numerically and measured empirically. The Proximity-Coupled Rectangular Patch Microstrip Antenna is treated numerically.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Davis, William A. (committee member), Safaai-Jazi, Ahmad (committee member).
Subjects/Keywords: Antennas; Small Antennas; Low Profile; Hand-Held; Inverted-F; Microstrip
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APA (6th Edition):
Gobien, A. T. I. (1997). Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/36959
Chicago Manual of Style (16th Edition):
Gobien, Andrew Timothy III. “Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios.” 1997. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/36959.
MLA Handbook (7th Edition):
Gobien, Andrew Timothy III. “Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios.” 1997. Web. 22 Jan 2021.
Vancouver:
Gobien ATI. Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios. [Internet] [Masters thesis]. Virginia Tech; 1997. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/36959.
Council of Science Editors:
Gobien ATI. Investigation of Low Profile Antenna Designs for Use in Hand-Held Radios. [Masters Thesis]. Virginia Tech; 1997. Available from: http://hdl.handle.net/10919/36959
Virginia Tech
14.
Chembil Palat, Ramesh.
VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements.
Degree: MS, Electrical and Computer Engineering, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/35712
► Next generation wireless communications require transmission of reliable high data rate services. Second generation wireless communications systems use single-input multiple-output (SIMO) channel in the reverse…
(more)
▼ Next generation wireless communications require transmission of reliable high data rate services. Second generation wireless communications systems use single-input multiple-output (SIMO) channel in the reverse link, meaning one transmit antenna at the user terminal and multiple receive antennas at the base station. Recently, information theoretic research has shown an enormous potential growth in the capacity of wireless systems by using multiple antenna arrays at both ends of the link. Space-time coding exploits the spatial-temporal diversity provided by the multiple input multiple output (MIMO) channels, significantly increasing both system capacity and the reliability of the wireless link. The
Virginia Tech Space-Time Advanced Radio (VT-STAR) system presents a test bed to demonstrate the capabilities of space-time coding techniques in real-time. Core algorithms are implemented on Texas Instruments TMS320C67 Evaluation Modules (EVM). The radio frequency subsystem is composed of multi-channel transmitter and receiver chains implemented in hardware for over the air transmission. The capabilities of the MIMO channel are demonstrated in a non-line of sight (NLOS) indoor environment. Also to characterize the capacity gains in an indoor environment this test bed was modified to take channel measurements. This thesis reports the system design of VT-STAR and the channel capacity gains observed in an indoor environment for MIMO channels.
Advisors/Committee Members: Reed, Jeffrey Hugh (committeechair), Stutzman, Warren L. (committee member), Woerner, Brian D. (committee member).
Subjects/Keywords: MIMO (Multiple input multiple output ); VT-STAR (Virginia Tech space-time advanced radiio)
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APA (6th Edition):
Chembil Palat, R. (2002). VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35712
Chicago Manual of Style (16th Edition):
Chembil Palat, Ramesh. “VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements.” 2002. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/35712.
MLA Handbook (7th Edition):
Chembil Palat, Ramesh. “VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements.” 2002. Web. 22 Jan 2021.
Vancouver:
Chembil Palat R. VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/35712.
Council of Science Editors:
Chembil Palat R. VT-STAR design and implementation of a test bed for differential space-time block coding and MIMO channel measurements. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/35712
Virginia Tech
15.
Haidara, Fatim M.
Rain scatter interference in satellite links.
Degree: MS, Electrical Engineering, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/43752
► Scattering by rain in addition to inducing attenuation and depolarization in satellite links can create intersystem interference. This type of interference was investigated extensively…
(more)
▼ Scattering by rain in addition to inducing attenuation and depolarization in satellite links
can create intersystem interference. This type of interference was investigated extensively in
the 1970's for terrestrial links, but little has been done to study its effects on modern and
future satellite links. This thesis reports on studies of the potential interference created by the
scattering of an uplink signal into an adjacent satellite and the inverse case where a downlink
signal is scattered into the earth station of an adjacent satellite system. The thesis describes
the rain medium in a way which emphasizes the computation of the needed single-drop
scattering coefficients using the extended boundary condition method (EBCM). The
development of the experimental and theoretical study of rain scattering interference is then
reviewed. Three computation methods for the interfering power are presented and compared.
The first one, based on the radiative transfer equation, includes multiple scattering
considerations, while the two other techniques take only the first order multiple scattering into
account. The impact of such interference is then studied and an experiment involving the
OLYMPUS and ACTS spacecraft is proposed.
Advisors/Committee Members: Bostian, Charles W. (committeechair), Stutzman, Warren L. (committee member), Pratt, Timothy J. (committee member).
Subjects/Keywords: Electromagnetic waves; LD5655.V855 1988.H338
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APA (6th Edition):
Haidara, F. M. (1988). Rain scatter interference in satellite links. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43752
Chicago Manual of Style (16th Edition):
Haidara, Fatim M. “Rain scatter interference in satellite links.” 1988. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/43752.
MLA Handbook (7th Edition):
Haidara, Fatim M. “Rain scatter interference in satellite links.” 1988. Web. 22 Jan 2021.
Vancouver:
Haidara FM. Rain scatter interference in satellite links. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/43752.
Council of Science Editors:
Haidara FM. Rain scatter interference in satellite links. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/43752
Virginia Tech
16.
Aprea, Matthew.
A model for predicting indoor signal levels of satellite transmitted signals.
Degree: MS, Electrical Engineering, 1995, Virginia Tech
URL: http://hdl.handle.net/10919/44015
► Several possible approaches to creating a model for predicting satellite signal levels inside buildings are examined. These models make use of resonant cavity modes…
(more)
▼ Several possible approaches to creating a model for predicting satellite signal levels inside
buildings are examined. These models make use of resonant cavity modes and vector ray
addition. The cavity mode approach yields inconclusive results because of a problem with
uniqueness, there are too many potential modes and no obvious way to decide between
them. The ray model uses vector representation. It tracks changes, and combines rays at
the receiver. Signal levels are normalized to free space values. An algorithm for the
construction of such a model is developed and results are obtained. A three ray model,
incorporating LOS, floor, and ceiling reflected rays gives reasonable agreement with
experimental data. The types of information needed are the room height, the receiver
height, if the receiver is in the vicinity of a window, and the elevation angle of the satellite.
This model shows that a user has to move only a small distance to find an area where
fading is brought to acceptable levels.
Advisors/Committee Members: Bostian, Charles W. (committeechair), Woerner, Brian D. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: satellite signals; LD5655.V855 1995.A674
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APA (6th Edition):
Aprea, M. (1995). A model for predicting indoor signal levels of satellite transmitted signals. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44015
Chicago Manual of Style (16th Edition):
Aprea, Matthew. “A model for predicting indoor signal levels of satellite transmitted signals.” 1995. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/44015.
MLA Handbook (7th Edition):
Aprea, Matthew. “A model for predicting indoor signal levels of satellite transmitted signals.” 1995. Web. 22 Jan 2021.
Vancouver:
Aprea M. A model for predicting indoor signal levels of satellite transmitted signals. [Internet] [Masters thesis]. Virginia Tech; 1995. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/44015.
Council of Science Editors:
Aprea M. A model for predicting indoor signal levels of satellite transmitted signals. [Masters Thesis]. Virginia Tech; 1995. Available from: http://hdl.handle.net/10919/44015
Virginia Tech
17.
Call, John B.
Large-signal characterization and modeling of nonlinear devices using scattering parameters.
Degree: MS, Electrical and Computer Engineering, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/35548
► Characterization and modeling of devices at high drive levels often requires specialized equipment and measurement techniques. Many large-signal devices will never have traditional nonlinear models…
(more)
▼ Characterization and modeling of devices at high drive levels often requires specialized equipment and measurement techniques. Many large-signal devices will never have traditional nonlinear models because model development is expensive and time-consuming. Due to the complexity of the device or the size of the application market, nonlinear modeling efforts may not be cost effective. Scattering parameters, widely used for small-signal passive and active device characterization, have received only cursory consideration for large-signal nonlinear device characterization due to technical and theoretical issues. We review the theory of S-parameters, active device characterization, and previous efforts to use S-parameters with large-signal nonlinear devices.
A robust, calibrated vector-measurement system is used to obtain device scattering parameters as a function of drive level. The unique measurement system architecture allows meaningful scattering parameter measurements of large-signal nonlinear devices, overcoming limitations reported by previous researchers.
A three-port S-parameter device model, with a nonlinear reflection coefficient terminating the third port, can be extracted from scattering parameters measured as a function of drive level. This three-port model provides excellent agreement with device measurements across a wide range of drive conditions. The model is used to simulate load-pull data for various drive levels which are compared to measured data.
Advisors/Committee Members: Davis, William A. (committeechair), Sweeney, Dennis G. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: microwave measurement; load-pull; black box model; S-parameters
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APA (6th Edition):
Call, J. B. (2002). Large-signal characterization and modeling of nonlinear devices using scattering parameters. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35548
Chicago Manual of Style (16th Edition):
Call, John B. “Large-signal characterization and modeling of nonlinear devices using scattering parameters.” 2002. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/35548.
MLA Handbook (7th Edition):
Call, John B. “Large-signal characterization and modeling of nonlinear devices using scattering parameters.” 2002. Web. 22 Jan 2021.
Vancouver:
Call JB. Large-signal characterization and modeling of nonlinear devices using scattering parameters. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/35548.
Council of Science Editors:
Call JB. Large-signal characterization and modeling of nonlinear devices using scattering parameters. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/35548
Virginia Tech
18.
Davis, Bradley A.
A clutter power computation procedure for airborne Doppler radar.
Degree: MS, Electrical Engineering, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/53722
► This report presents a general procedure for estimating the average clutter power received by an airborne Doppler radar as a function of time and frequency.…
(more)
▼ This report presents a general procedure for estimating the average clutter power received by an airborne Doppler radar as a function of time and frequency. Its purpose is to construct the received power waveform at the output of a matched filter for use in the development of clutter maps related to Doppler signal processing.
In developing the algorithm, several of its features are given close examination; this includes a numerical and analytical justification for the azimuth to Doppler coordinate transformation, and the power spectrum returned to the airborne Doppler radar from the surface it illuminates. This algorithm produces a continuous power returned waveform versus time. Hence, this algorithm has the flexibility to accept any surface radar cross section, antenna gain, and pulse type (a matched filter receiver is assumed) as a function of range and azimuth.
It was discovered that the algorithm could be executed with significantly less computer time if the integration surface area was reduced by exploiting some physical insight. In addition, it was discovered through example that the refracting effects of the Earth's atmosphere become important as the radar's beam approaches the horizon.
Finally, return power waveforms are studied for two different situations: near nadir pointing, and near horizon pointing. The manner in which the matched filter ambiguity function and the spectrum of backscattered power combine to produce these waveforms is examined.
Advisors/Committee Members: Brown, Gary S. (committeechair), Stutzman, Warren L. (committee member), Pratt, T. P. (committee member).
Subjects/Keywords: LD5655.V855 1988.D384; Doppler radar; Radar in aeronautics
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APA (6th Edition):
Davis, B. A. (1988). A clutter power computation procedure for airborne Doppler radar. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/53722
Chicago Manual of Style (16th Edition):
Davis, Bradley A. “A clutter power computation procedure for airborne Doppler radar.” 1988. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/53722.
MLA Handbook (7th Edition):
Davis, Bradley A. “A clutter power computation procedure for airborne Doppler radar.” 1988. Web. 22 Jan 2021.
Vancouver:
Davis BA. A clutter power computation procedure for airborne Doppler radar. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/53722.
Council of Science Editors:
Davis BA. A clutter power computation procedure for airborne Doppler radar. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/53722
Virginia Tech
19.
Huynh, Minh-Chau Thu.
A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications.
Degree: MS, Electrical and Computer Engineering, 2000, Virginia Tech
URL: http://hdl.handle.net/10919/35477
► <p align=justifiy> In recent years, the demand for compact handheld communication devices has grown significantly. Devices having internal antennas have appeared to fill this need.…
(more)
▼ <p align=justifiy>
In recent years, the demand for compact handheld communication devices has grown significantly. Devices having internal antennas have appeared to fill this need. Antenna size is a major factor that limits device miniaturization. In the past few years, new designs based on the microstrip antennas (MSA) and planar inverted-F antennas have been used for handheld wireless devices because these antennas have low-profile geometry and can be embedded into the devices.
<p align=justifiy>
New wireless applications requiring operation in more than one frequency band are emerging. Dual-band and tri-band phones have gained popularity because of the multiple frequency bands used for wireless applications. One prominent application is to include bluetooth, operating band at 2.4 GHz, for short-range wireless use.
<p align=justifiy>
This thesis examines two antennas that are potential candidates for small and low-profile structures: microstrip antennas and planar inverted-F antennas. Two techniques for widening the antenna impedance bandwidth are examined by adding parasitic elements. Reducing antenna size generally degrades antenna performance. It is therefore important to also examine the fundamental limits and parameter tradeoffs involved in size reduction. In the handheld environment, antennas are mounted on a small ground plane. Ground plane size effects on antennas are investigated and the results from a thorough numerical study on the performance of a PIFA with various ground planes sizes and shapes is reported. Finally, a new wideband compact PIFA antenna (WC-PIFA) is proposed. Preliminary work is presented along with numerical and experimental results for various environments such as free space, plastic casing, and the proximity of a hand. This new antenna covers frequencies from 1700 MHz to 2500 MHz, which basically include the following operating bands: DCS-1800m PCS-1900, IMT-2000, ISM, and Bluetooth.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Davis, William A. (committee member), Sweeney, Dennis G. (committee member).
Subjects/Keywords: microstrip; small antennas; PIFA; wideband antennas; ground plane effects; antennas; planar inverted-f; low-profile
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APA (6th Edition):
Huynh, M. T. (2000). A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/35477
Chicago Manual of Style (16th Edition):
Huynh, Minh-Chau Thu. “A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications.” 2000. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/35477.
MLA Handbook (7th Edition):
Huynh, Minh-Chau Thu. “A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications.” 2000. Web. 22 Jan 2021.
Vancouver:
Huynh MT. A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications. [Internet] [Masters thesis]. Virginia Tech; 2000. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/35477.
Council of Science Editors:
Huynh MT. A Numerical and Experimental Investigation of Planar Inverted-F Antennas for Wireless Applications. [Masters Thesis]. Virginia Tech; 2000. Available from: http://hdl.handle.net/10919/35477
Virginia Tech
20.
Lu, Shu.
Design, fabrication, and characterization of a wideband microwave balun.
Degree: MS, Electrical Engineering, 1990, Virginia Tech
URL: http://hdl.handle.net/10919/42079
► A wideband microwave balun is designed to adapt unbalanced to balanced transmission line networks. The balun is realized by a planar microstrip line configuration…
(more)
▼ A wideband microwave balun is designed to adapt unbalanced to balanced
transmission line networks. The balun is realized by a planar microstrip line
configuration on a double copper c1added teflon-ceramic C0I11posite board. The
microstrip line conductor pattern was formed on the board using the chemical
etching process. The fabricated balun is measured and evaluated in both the
time domain and frequency domain, indicating a 5 GHz bandwidth. The time
domain modeling technique is used to characterize the balun's performance.
Based on physical analysis of the balun's configuration, the discontinuities
through the transmission paths are modeled as distributed and lumped elements,
resulting in an equivalent network model for the balun structure. The obtained
model successfully simulates the balun's performance.
Advisors/Committee Members: Stutzman, Warren L. (committee member), Elshabini-Riad, Aicha A. (committeecochair), Riad, Sedki Mohamed (committeecochair).
Subjects/Keywords: Microwave devices; LD5655.V855 1990.L8
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APA (6th Edition):
Lu, S. (1990). Design, fabrication, and characterization of a wideband microwave balun. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/42079
Chicago Manual of Style (16th Edition):
Lu, Shu. “Design, fabrication, and characterization of a wideband microwave balun.” 1990. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/42079.
MLA Handbook (7th Edition):
Lu, Shu. “Design, fabrication, and characterization of a wideband microwave balun.” 1990. Web. 22 Jan 2021.
Vancouver:
Lu S. Design, fabrication, and characterization of a wideband microwave balun. [Internet] [Masters thesis]. Virginia Tech; 1990. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/42079.
Council of Science Editors:
Lu S. Design, fabrication, and characterization of a wideband microwave balun. [Masters Thesis]. Virginia Tech; 1990. Available from: http://hdl.handle.net/10919/42079
Virginia Tech
21.
Kim, Jeong I.
Log-Periodic Loop Antennas.
Degree: MS, Electrical and Computer Engineering, 1999, Virginia Tech
URL: http://hdl.handle.net/10919/34392
► The Log-Periodic Loop Antenna with Ground Reflector (LPLA-GR) is investigated as a new type of antenna, which provides wide bandwidth, broad beamwidth, and high gain.…
(more)
▼ The Log-Periodic Loop Antenna with Ground Reflector (LPLA-GR) is investigated as a new type of antenna, which provides wide bandwidth, broad beamwidth, and high gain. This antenna has smaller transverse dimensions (by a factor of 2/pi) than a log-periodic dipole antenna with comparable radiation characteristics. Several geometries with different parameters are analyzed numerically using ESP code, which is based on the method of moments. A LPLA-GR with 6 turns and a cone angle of 30* offers the most promising radiation characteristics. This antenna yields 47.6 % gain bandwidth and 12 dB gain according to the numerical analysis. The LPLA-GR also provides linear polarization and unidirectional patterns.
Three prototype antennas were constructed and measured in the
Virginia Tech Antenna Laboratory. Far-field patterns and input impedance were measured over a wide range of frequencies. The measured results agree well with the calculated results. Because of its wide bandwidth, high gain, and small size, the LPLA is expected to find applications as feeds for reflector antennas, as detectors in EMC scattering range, and as mobile communication antennas.
Advisors/Committee Members: Safaai-Jazi, Ahmad (committeechair), Stutzman, Warren L. (committee member), Poon, Ting-Chung (committee member).
Subjects/Keywords: Log-Periodic Loop Antenna; Log-Periodic Dipole Antenna; Ground Reflector; ESP; Frequency Independent Antenna
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APA (6th Edition):
Kim, J. I. (1999). Log-Periodic Loop Antennas. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/34392
Chicago Manual of Style (16th Edition):
Kim, Jeong I. “Log-Periodic Loop Antennas.” 1999. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/34392.
MLA Handbook (7th Edition):
Kim, Jeong I. “Log-Periodic Loop Antennas.” 1999. Web. 22 Jan 2021.
Vancouver:
Kim JI. Log-Periodic Loop Antennas. [Internet] [Masters thesis]. Virginia Tech; 1999. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/34392.
Council of Science Editors:
Kim JI. Log-Periodic Loop Antennas. [Masters Thesis]. Virginia Tech; 1999. Available from: http://hdl.handle.net/10919/34392
Virginia Tech
22.
Evers, Brent A.
ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data.
Degree: MS, Electrical Engineering, 1994, Virginia Tech
URL: http://hdl.handle.net/10919/46112
► Virginia Tech has recently developed and constructed seven ground terminals for use in a propagation experiment employing the Advanced Communications Technology Satellite. This satellite…
(more)
▼ Virginia Tech has recently developed and constructed seven ground terminals for use in a
propagation experiment employing the Advanced Communications Technology Satellite.
This satellite was deployed by NASA in September of 1993. The ground terminals are
used in the study of propagation effects caused by the atmosphere for 20 and 30 GHz
signals. Each of these terminals contains one total power radiometer for each frequency.
These radiometers are used to set clear sky attenuation reference levels for satellite beacon
calibration. This thesis describes the design, implementation and testing of the
radiometers built at
Virginia Tech.
In addition, a mathematical algorithm used for the prediction of clear sky attenuation
along satellite paths is tested for correlation with radiometer predicted clear sky
attenuation. Test data is compared to determine if the algorithm might serve as a
radiometer replacement in future propagation experiments or other applications.
Advisors/Committee Members: Pratt, Timothy J. (committeechair), Stutzman, Warren L. (committee member), Brown, Gary S. (committee member).
Subjects/Keywords: Meteorological instruments; LD5655.V855 1994.E947
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APA (6th Edition):
Evers, B. A. (1994). ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/46112
Chicago Manual of Style (16th Edition):
Evers, Brent A. “ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data.” 1994. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/46112.
MLA Handbook (7th Edition):
Evers, Brent A. “ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data.” 1994. Web. 22 Jan 2021.
Vancouver:
Evers BA. ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data. [Internet] [Masters thesis]. Virginia Tech; 1994. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/46112.
Council of Science Editors:
Evers BA. ACTS radiometers and a comparison of atmospheric attenuation derived form temperature-humidity and radiometric data. [Masters Thesis]. Virginia Tech; 1994. Available from: http://hdl.handle.net/10919/46112
Virginia Tech
23.
Kelley, David Frederick.
Analysis of phased array antenna radiation patterns including mutual coupling.
Degree: MS, Electrical Engineering, 1990, Virginia Tech
URL: http://hdl.handle.net/10919/46438
► Methods of expressing the radiation patterns of phased arrays in closed form that include the effects of radiated mutual coupling are investigated. The two…
(more)
▼ Methods of expressing the radiation patterns of phased arrays in closed form that include the effects
of radiated mutual coupling are investigated. The two basic methods considered are the classical
array analysis method and the active element pattern methods. The theoretical derivations of the
active element pattern methods are presented and the various types of active element patterns are
defined. Also, a new method based on active element patterns, the hybrid active element pattern
method, is introduced which accurately predicts the patterns of small and moderately-sized arrays
of equally-spaced elements. Arrays of center-fed dipoles are considered in this study since dipole
arrays can be fully characterized, including mutual coupling, using modem numerical
electromagnetic analysis codes, thus allowing verification of the array analysis methods presented
here. The results are general, however, and may be applied to arrays of any type of element. The
array patterns computed using the classical analysis method and the active element pattern methods
are compared to those computed using ideal array analysis and the highly-accurate numerical codes.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Davis, William A. (committee member), Brown, Gary S. (committee member).
Subjects/Keywords: Antenna arrays; LD5655.V855 1990.K456
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APA (6th Edition):
Kelley, D. F. (1990). Analysis of phased array antenna radiation patterns including mutual coupling. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/46438
Chicago Manual of Style (16th Edition):
Kelley, David Frederick. “Analysis of phased array antenna radiation patterns including mutual coupling.” 1990. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/46438.
MLA Handbook (7th Edition):
Kelley, David Frederick. “Analysis of phased array antenna radiation patterns including mutual coupling.” 1990. Web. 22 Jan 2021.
Vancouver:
Kelley DF. Analysis of phased array antenna radiation patterns including mutual coupling. [Internet] [Masters thesis]. Virginia Tech; 1990. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/46438.
Council of Science Editors:
Kelley DF. Analysis of phased array antenna radiation patterns including mutual coupling. [Masters Thesis]. Virginia Tech; 1990. Available from: http://hdl.handle.net/10919/46438
Virginia Tech
24.
Dietze, Kai.
Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel.
Degree: MS, Electrical and Computer Engineering, 2001, Virginia Tech
URL: http://hdl.handle.net/10919/32412
► This report, presents an analytical framework for analyzing two-branch diversity systems for a Rayleigh fading channel. In many cases the fading received at both branches…
(more)
▼ This report, presents an analytical framework for analyzing two-branch diversity systems for a Rayleigh fading channel. In many cases the fading received at both branches (i.e. a two-antenna element system) is correlated because of the proximity of the antenna elements to each other. It is also not uncommon for a diversity system to use antennas with different patterns or polarizations, this usually results in differences in average signal-to-noise ratios at both branches depending on which element is better matched to the signal environment. As will be shown, the performance of a diversity system depends greatly on the envelope correlation, average power imbalance and the combining scheme used on both branches.
An analytical expression for the probability density function of the signal-to-noise ratio at the output of a two-branch maximal ratio and selection diversity system is developed in this report. The two branches are assumed to be Rayleigh fading, correlated, as well as of unequal signal-to-noise ratios. Measurements were made in Rayleigh fading channels and compared to the analytical results. The analytical cumulative distribution functions (derived using probability distributions) were found to be within 1 dB of the measured results (statistics obtained from time combining) for both maximal ratio and selection diversity attesting to the validity of the analytic results. Also developed in this report are the exact analytical average probabilities of symbol error for coherent BPSK and coherent QPSK before and after maximal ratio combining for this environment. The diversity gain for selection, maximal ratio, and equal gain combining for the 10% probability level is presented as a function of power imbalance and correlation between branches for a two-branch Rayleigh diversity system
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Woerner, Brain D. (committee member), Reed, Jeffrey Hugh (committee member).
Subjects/Keywords: Maximal Ratio; Antenna Diversity; Selection Diversity; BPSK; Correlated Channels; Rayleigh Channel; Diversity Gain; QPSK
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APA (6th Edition):
Dietze, K. (2001). Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/32412
Chicago Manual of Style (16th Edition):
Dietze, Kai. “Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel.” 2001. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/32412.
MLA Handbook (7th Edition):
Dietze, Kai. “Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel.” 2001. Web. 22 Jan 2021.
Vancouver:
Dietze K. Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel. [Internet] [Masters thesis]. Virginia Tech; 2001. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/32412.
Council of Science Editors:
Dietze K. Analysis of a Two-Branch Maximal Ratio and Selection Diversity System with Unequal Branch Powers and Correlated Inputs for a Rayleigh Fading Channel. [Masters Thesis]. Virginia Tech; 2001. Available from: http://hdl.handle.net/10919/32412
Virginia Tech
25.
Huie, Keith C.
Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates.
Degree: MS, Electrical and Computer Engineering, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/30898
► The purpose of this thesis is to investigate a novel method to develop broadband microstrip (patch) antennas using substrates containing photonic crystals. Photonic crystals are…
(more)
▼ The purpose of this thesis is to investigate a novel method to develop broadband microstrip (patch) antennas using substrates containing photonic crystals. Photonic crystals are a class of periodic dielectric, metallic, or composite structures that when introduced to an electromagnetic signal can exhibit a forbidden band of frequencies (or bandgap) in which the incident signal destructively interferes and thus is unable to propagate. It is proposed that such photonic crystals will reduce surface waves and prohibit the formation of substrate modes, which are commonly known inhibitors of patch antenna designs. By reducing or eliminating the effects of these electromagnetic inhibitors with photonic crystals, a broadband response can be obtained from inherently narrowband antennas. In addition, it is also proposed that the behavior of the photonic crystals will lead to a reduction in pattern sidelobes resulting in improvements in radiation pattern front-to-back ratio and overall antenna efficiency. This research is verified through analytical simulations and experimental investigations in the
Virginia Tech anaechoic chamber.
Advisors/Committee Members: Claus, Richard O. (committeechair), Stutzman, Warren L. (committee member), Saraf, Ravi F. (committee member).
Subjects/Keywords: photonic crystals; microstrip antennas; surface waves; broadband; bandgap
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APA (6th Edition):
Huie, K. C. (2002). Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/30898
Chicago Manual of Style (16th Edition):
Huie, Keith C. “Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates.” 2002. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/30898.
MLA Handbook (7th Edition):
Huie, Keith C. “Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates.” 2002. Web. 22 Jan 2021.
Vancouver:
Huie KC. Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/30898.
Council of Science Editors:
Huie KC. Microstrip Antennas: Broadband Radiation Patterns Using Photonic Crystal Substrates. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/30898
Virginia Tech
26.
Henkle, Thomas Grove III.
Performance characteristics of a multiple use Ku-band satellite network.
Degree: MS, Electrical Engineering, 1989, Virginia Tech
URL: http://hdl.handle.net/10919/44646
► Construction of a Ku-band earth station was completed in August 1989 at the teleport in the Corporate Research Center of Virginia Polytechnic Institute and State…
(more)
▼ Construction of a Ku-band earth station was completed in August 1989 at the teleport in the
Corporate Research Center of
Virginia Polytechnic Institute and State University. At that time
specific applications for the terminal were being determined. Several satellite networks which can
use the Ku-band earth station are explored in this thesis. System level designs are presented for
each network. The anticipated performance of the network during clear sky conditions and during
periods of rain fade conditions are calculated. To aid in these calculations the software package
LAMP was developed.
detailed system design of a VSAT network is given in later chapters. The development of
VSAT networks considers multiple access and data traffic control protocols. VSAT network
performance under various traffic conditions also is determined.
Advisors/Committee Members: Rappaport, Theodore S. (committee member), Pratt, Timothy J. (committeecochair), Stutzman, Warren L. (committeecochair).
Subjects/Keywords: Artificial satellites in telecommunication; LD5655.V855 1989.H465
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APA (6th Edition):
Henkle, T. G. I. (1989). Performance characteristics of a multiple use Ku-band satellite network. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/44646
Chicago Manual of Style (16th Edition):
Henkle, Thomas Grove III. “Performance characteristics of a multiple use Ku-band satellite network.” 1989. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/44646.
MLA Handbook (7th Edition):
Henkle, Thomas Grove III. “Performance characteristics of a multiple use Ku-band satellite network.” 1989. Web. 22 Jan 2021.
Vancouver:
Henkle TGI. Performance characteristics of a multiple use Ku-band satellite network. [Internet] [Masters thesis]. Virginia Tech; 1989. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/44646.
Council of Science Editors:
Henkle TGI. Performance characteristics of a multiple use Ku-band satellite network. [Masters Thesis]. Virginia Tech; 1989. Available from: http://hdl.handle.net/10919/44646
Virginia Tech
27.
Kirchner, David J.
Removal of interference inherent in the lens radar system.
Degree: MS, Electrical Engineering, 1988, Virginia Tech
URL: http://hdl.handle.net/10919/45885
► The NASA GSFC/Wallops Flight Facility focused radar system employed a large (43 cm diameter) dielectric focusing lens such that the water surface (target) was…
(more)
▼ The NASA GSFC/Wallops Flight Facility focused radar system employed a
large (43 cm diameter) dielectric focusing lens such that the water surface (target)
was illuminated by a small radar spot (~1.25 cm diameter). With this small spot size,
surface profiles and probability density functions could be generated. The system
suffered an interference problem which made reliable data collection impossible.
Study showed that the system had to be operated bistatically in order to reduce the
effects of interference found to be caused by signal leaking directly from the transmitter
to the receiver. Since the system was operated in a confined space (the wind-wavetank), multipath was found to generate interference signals. The multipath interference was reduced via strategic placement of radio frequency absorber. A
comparison was made between experimental results with the original system and the
final bistatic system to demonstrate the effect of the reduction in interference. A
model was also derived for the direct leakage interference and used to explain experimental
results.
Advisors/Committee Members: Brown, Gary S. (committeechair), Pratt, Timothy J. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: Radar receiving apparatus.; LD5655.V855 1988.K572
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APA (6th Edition):
Kirchner, D. J. (1988). Removal of interference inherent in the lens radar system. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/45885
Chicago Manual of Style (16th Edition):
Kirchner, David J. “Removal of interference inherent in the lens radar system.” 1988. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/45885.
MLA Handbook (7th Edition):
Kirchner, David J. “Removal of interference inherent in the lens radar system.” 1988. Web. 22 Jan 2021.
Vancouver:
Kirchner DJ. Removal of interference inherent in the lens radar system. [Internet] [Masters thesis]. Virginia Tech; 1988. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/45885.
Council of Science Editors:
Kirchner DJ. Removal of interference inherent in the lens radar system. [Masters Thesis]. Virginia Tech; 1988. Available from: http://hdl.handle.net/10919/45885
Virginia Tech
28.
Dishman, William Keith.
Estimation of rain attenuation on earth-space millimeter wave communications links.
Degree: MS, Electrical Engineering, 1982, Virginia Tech
URL: http://hdl.handle.net/10919/33525
Subjects/Keywords: Millimeter waves; LD5655.V855 1982.D573
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APA (6th Edition):
Dishman, W. K. (1982). Estimation of rain attenuation on earth-space millimeter wave communications links. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/33525
Chicago Manual of Style (16th Edition):
Dishman, William Keith. “Estimation of rain attenuation on earth-space millimeter wave communications links.” 1982. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/33525.
MLA Handbook (7th Edition):
Dishman, William Keith. “Estimation of rain attenuation on earth-space millimeter wave communications links.” 1982. Web. 22 Jan 2021.
Vancouver:
Dishman WK. Estimation of rain attenuation on earth-space millimeter wave communications links. [Internet] [Masters thesis]. Virginia Tech; 1982. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/33525.
Council of Science Editors:
Dishman WK. Estimation of rain attenuation on earth-space millimeter wave communications links. [Masters Thesis]. Virginia Tech; 1982. Available from: http://hdl.handle.net/10919/33525
Virginia Tech
29.
Caswell, Eric D.
Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions.
Degree: MS, Electrical and Computer Engineering, 1998, Virginia Tech
URL: http://hdl.handle.net/10919/37001
► Typically wire antenna structures are modeled by approximating curved structures with straight wire segments. The straight wire approximation yields accurate results, but often requires a…
(more)
▼ Typically wire antenna structures are modeled by approximating curved structures with straight wire segments. The straight wire approximation yields accurate results, but often requires a large number of segments to adequately approximate the antenna geometry. The large number of straight wire segments or unknowns requires a large amount of memory and time to solve for the currents on the antenna. By using curved segments which exactly describe the contour of the antenna geometry the number of unknowns can be reduced, thus allowing for bigger problems to be solved accurately. This thesis focuses on the analysis of a helix antenna. The Method of Moments is used to solve for the currents on the antenna, and both the triangle basis and pulse testing functions exactly follow the contour of the helix antenna. The thin wire approximation is used throughout the analysis. The helix is assumed to be oriented along the z-axis with an optional perfect electric conductor (PEC) ground plane in the x-y plane. For simplicity, a delta gap source model is used. Straight feed wires may also be added to the helix, and are modeled similarly to the helix by the Method of Moments with triangular basis and pulse testing functions.
The primary validation of the curved wire approach is through a comparison with MININEC and NEC of the convergence properties of the input impedance of the antenna versus the number of unknowns. The convergence tests show that significantly fewer unknowns are needed to accurately predict the input impedance of the helix, particularly for the normal mode helix. This approach is also useful in the analysis of the axial mode helix where the current changes significantly around one turn. Because of the varying current distribution, the improvement of impedance convergence with curved segments is not as significant for the axial mode helix. However, radiation pattern convergence improvement is found. Multiple feed structures for the axial mode helix are also investigated. In general, the many straight wire segments, and thus unknowns, that are needed to accurately approximate the current around one turn can be greatly reduced by the using the curved segment method.
Advisors/Committee Members: Davis, William A. (committeechair), Brown, Gary S. (committee member), Stutzman, Warren L. (committee member).
Subjects/Keywords: Helix; Method of Moments; Curved Segments
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APA (6th Edition):
Caswell, E. D. (1998). Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/37001
Chicago Manual of Style (16th Edition):
Caswell, Eric D. “Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions.” 1998. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/37001.
MLA Handbook (7th Edition):
Caswell, Eric D. “Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions.” 1998. Web. 22 Jan 2021.
Vancouver:
Caswell ED. Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions. [Internet] [Masters thesis]. Virginia Tech; 1998. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/37001.
Council of Science Editors:
Caswell ED. Analysis of a Helix Antenna Using a Moment Method Approach With Curved Basis and Testing Functions. [Masters Thesis]. Virginia Tech; 1998. Available from: http://hdl.handle.net/10919/37001
Virginia Tech
30.
Joshi, Gaurav Gaurang.
Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz.
Degree: MS, Electrical and Computer Engineering, 2002, Virginia Tech
URL: http://hdl.handle.net/10919/43757
► Mobile arrays employing diversity combining and adaptive beamforming techniques overcome multipath fading, improve coverage, and increase capacity in wireless communications systems. In this thesis, diversity…
(more)
▼ Mobile arrays employing diversity combining and adaptive beamforming techniques overcome multipath fading, improve coverage, and increase capacity in wireless communications systems. In this thesis, diversity combining and adaptive beamforming performance of different four element arrays for mobile (vehicular speed) and portable (pedestrian speed) terminals is investigated. The performance of four element arrays with different configurations and with different element patterns is compared using the square array of four half-wave dipole elements as the baseline. Results from diversity and beamforming measurements, performed in urban and suburban environments for both line-of-sight (LOS) and obstructed multipath channels are used to analyze and compare the performances of different four element arrays. At cumulative probabilities of 10%, 1% and 0.1%, diversity gain and improvement in signal-to-interference-plus-noise-ratio (SINR) are calculated from the diversity combining measurements and interference rejection measurements respectively.
Experimental results illustrating the dependence of diversity gain on power imbalance, envelope correlation and diversity-combining scheme are presented. Measurements were performed at 2.05 GHz using the handheld antenna array testbed (HAAT). Low profile linear arrays are shown to provide diversity gain values of 5 to 8 dB and 11 to 16 dB, respectively for switched and maximal ratio combining at the 99% reliability level in non-line-of-sight urban channel. Interference cancellation of 24 to 28 dB was recorded in urban and suburban line-of-sight (LOS) channels for the sectorized square array. Results of vehicular measurements with the arrays mounted on a ground plane supported above the vehicle roof are also reported.
Advisors/Committee Members: Stutzman, Warren L. (committeechair), Reed, Jeffrey Hugh (committee member), Sweeney, Dennis G. (committee member).
Subjects/Keywords: rayleigh channel; switched diversity; maximal ratio combining; antenna diversity; vehicular measurements; interference rejection; mobile arrays; diversity gain
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Joshi, G. G. (2002). Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/43757
Chicago Manual of Style (16th Edition):
Joshi, Gaurav Gaurang. “Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz.” 2002. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/43757.
MLA Handbook (7th Edition):
Joshi, Gaurav Gaurang. “Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz.” 2002. Web. 22 Jan 2021.
Vancouver:
Joshi GG. Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz. [Internet] [Masters thesis]. Virginia Tech; 2002. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/43757.
Council of Science Editors:
Joshi GG. Four Branch Diversity Combining and Adaptive Beamforming Measurements Using Mobile Arrays at 2.05 GHz. [Masters Thesis]. Virginia Tech; 2002. Available from: http://hdl.handle.net/10919/43757
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