+publisher:"University of Oklahoma" +contributor:("Ruyle, Jessica")

University of Oklahoma

1. Dunn, Zachary. Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars.

Degree: PhD, 2016, University of Oklahoma

URL: http://hdl.handle.net/11244/34587

► Many new and interesting radar operational modes and techniques are being explored to maximize the efficiency and utility of next-generation radar systems while complying with… (more)

▼ Many new and interesting radar operational modes and techniques are being explored to maximize the efficiency and utility of next-generation radar systems while complying with increasingly stringent operational and budgeting requirements. This dissertation's aim is to analyze and present possible techniques to help maximize the scientific value of measurements while complying with operational requirements through methods of physical transmission and exciting the target area, methods of processing the received waveforms, and methods of designing waveforms for a given system. In regard to methods of physical transmission and exciting the target area, this dissertation addresses unique problems that will be faced by next-generation radar systems utilizing simultaneous transmit and simultaneous receive operational modes in polarimetric active phased array architectures. This is accomplished through establishing mathematical representations of the received complex baseband waveforms for dual-polarimetric radar operation and analyzing the predicted behavior versus traditional polarimetric radar alternating transmit and simultaneous receive operation. In regard to methods of processing the received waveforms, pulse compression will undoubtedly be widely utilized in future radar systems due to the increase in range resolution that it provides for a given pulse length. Additionally, matched filtering allows the realization of simultaneously transmitted pseudo-orthogonal waveforms occupying the same spectral region that would be otherwise impossible. As a result, the mathematical basis of pulse compression is provided, and pulse compression effects are taken into account in all relevant system analyses in this manuscript. This dissertation arguably provides the most attention in regard to methods for designing and modifying waveforms for application in a given system. An analysis of common pulse compression waveforms for suitability in pseudo-orthogonal waveform sets is provided in addition to a novel method for designing polyphase coded waveform and non-linear frequency modulated waveform based pseudo-orthogonal waveform sets utilizing particle swarm optimization. Additionally, for the first time, research is presented on the full design and application methods for digital predistortion of wideband solid state radar amplifiers. Digital predistortion methods and results are presented for both the impedance matched high power amplifier case and for the varying load impedance case that can be expected to be encountered in radar systems utilizing electronic beamsteering in active phased array architectures. Overall, this dissertation's aim is to provide relevant results from conducted research in the form of analysis and novel design methods that can be applied in both the design and operation of next-generation radar systems to maximize utility and scientific data quality while operating within given system and environmental specifications. Advisors/Committee Members: Yeary, Mark (advisor), Fulton, Caleb (committee member), Goodman, Nathan (committee member), Ruyle, Jessica (committee member), Biggerstaff, Michael (committee member).

Subjects/Keywords: Digital Predistortion; Phased Array; Polarimetric; Engineering, Electronics and Electrical.

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APA (6^th Edition):

Dunn, Z. (2016). Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/34587

Chicago Manual of Style (16^th Edition):

Dunn, Zachary. “Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars.” 2016. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/34587.

MLA Handbook (7^th Edition):

Dunn, Zachary. “Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars.” 2016. Web. 25 Jan 2021.

Vancouver:

Dunn Z. Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars. [Internet] [Doctoral dissertation]. University of Oklahoma; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/34587.

Council of Science Editors:

Dunn Z. Digital Predistortion of Pseudo-Orthogonal Wideband Waveforms for Dual-Polarimetric Phased Array Radars. [Doctoral Dissertation]. University of Oklahoma; 2016. Available from: http://hdl.handle.net/11244/34587

University of Oklahoma

2. Bhowmik, Lal Mohan. Applications of Floquet Analysis to Modern Phased Array Antennas.

Degree: PhD, 2019, University of Oklahoma

URL: http://hdl.handle.net/11244/321405

► Next generation radar technology is based on phased array technology and provides remarkable scanning flexibility and spatial search capability for the multifunction weather and air… (more)

▼ Next generation radar technology is based on phased array technology and provides remarkable scanning flexibility and spatial search capability for the multifunction weather and air surveillance radar systems. The future weather radar is comprised of thousands of antenna elements and requires strict polarization purity, grating lobe free system, low sidelobe levels, suppressed surface waves, low cross-polarization, with beam shape requirements. To address these demands is a serious challenge. Over the past few decades, phased array radar technology has been a tremendous advancement in search for future radar technology. With the blessing of modern computational electromagnetic tools, the theory behind the electromagnetic and circuit-level behavior of large-scale phased array system opened the door to analyze the wide variety of multi-layered, complex system of large arrays. However, numerous challenges still remained unsolved for large scale development. One such challenge in integrating a large phased array is the threat of grating lobes that are introduced by unavoidable disturbances to the periodic structure at the seams between mechanical sub-array modules. In particular, gaps in the ground plane may interrupt the natural currents between elements, leading to radiation from periodic sources that are spaced at regular distances that are typically many wavelengths apart. In order to quantify these grating lobe effects, an appropriate analysis framework and accurate model are of utmost importance. The model must capture all surface wave and mutual coupling between elements, and the analysis must have a clear formulation that allows for the calculation of worst-case grating lobe levels as well as differences in active reflection as a function of location within a sub-array. To accurately predict those effects, this dissertation work applied a modern method called Floquet framework, coupling with full wave solver to explore the grating lobe effects in infinite arrays of sub-arrays, with each physical sub-array potentially separated from the others by a gap or discontinuity in the ground plane. Calculations are then performed to extract active reflection coefficients and grating lobe levels from the resulting Floquet mode scattering parameters. Additionally, this Floquet framework is expanded from broadside to any scan angles in space. In the mathematical framework, the surface equivalence theorem based on Huygens’s equivalence principle is applied to authenticate its findings. From the simulation results, it is evident that the grating lobe amplitude level emerged to around 30 dB in the E-plane scan and E- plane grating lobes for a patch array. This is due to natural current disruption in between sub-arrays in the ground plane gap and it is very strong in the E-plane, leading to the potential for low-level grating lobe effects. The other planes and scan angles show less significant effects. It was found that the measurements qualitatively follow the simulated results. The Floquet-based method may therefore be used… Advisors/Committee Members: Fulton, Caleb (advisor), Remling, Christian (committee member), Bluestein, Howard (committee member), Goodman, Nathan (committee member), Sigmarsson, Hjalti (committee member), Ruyle, Jessica (committee member).

Subjects/Keywords: Scan blindness; Creeping waves; Cylindrical Electromagnetic Bandgap (EBG) structures; Floquet analysis; Grating lobe; MPAR; CPPAR; Phased array

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Bhowmik, L. M. (2019). Applications of Floquet Analysis to Modern Phased Array Antennas. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/321405

Chicago Manual of Style (16^th Edition):

Bhowmik, Lal Mohan. “Applications of Floquet Analysis to Modern Phased Array Antennas.” 2019. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/321405.

MLA Handbook (7^th Edition):

Bhowmik, Lal Mohan. “Applications of Floquet Analysis to Modern Phased Array Antennas.” 2019. Web. 25 Jan 2021.

Vancouver:

Bhowmik LM. Applications of Floquet Analysis to Modern Phased Array Antennas. [Internet] [Doctoral dissertation]. University of Oklahoma; 2019. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/321405.

Council of Science Editors:

Bhowmik LM. Applications of Floquet Analysis to Modern Phased Array Antennas. [Doctoral Dissertation]. University of Oklahoma; 2019. Available from: http://hdl.handle.net/11244/321405

University of Oklahoma

3. Wang, Bing. X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS.

Degree: PhD, 2016, University of Oklahoma

URL: http://hdl.handle.net/11244/34616

► This thesis describes research into the roles that metalloproteins and non-metalloproteins play in the biological inorganic/organic chemistry of common nitrogen oxides. There are three main… (more)

▼ This thesis describes research into the roles that metalloproteins and non-metalloproteins play in the biological inorganic/organic chemistry of common nitrogen oxides. There are three main chapters on this work: the first details the reactions of wild-type and mutant myoglobins (Mbs) in their interactions with nitrite and nitric oxide (NO), the second deals with these Mbs and their formation of bioorganometallic derivatives when reacted with arylhydrazines, and the third deals with an FMN-dependent nitroreductase enzyme and its reactions with the clinically relevant metronidazole drug. Mutations to the distal pocket in the active site of Mb were made; specifically, ferric-aqua derivatives of the mutants were expressed, purified, crystallized, and their crystal structures solved to 1.78-1.85 Å resolution. The proteins crystallized in either the P21 or P6 space groups. The crystals were soaked with nitrite to form their O-bonded MbIII(ONO) complexes whose structures were also solved to 1.57-1.85 Å resolution. In the case of the H64A distal pocket mutant missing the H-bonding amino-acid residue in the 64th position, a water bridge was observed to form linking the protein exterior with the bound nitrite ligand, thus replacing the expected wt H64 H-bonding feature. Further, we noted that the distal pocket Val68 residue adapted its conformation to accommodate the nitrite ligands in some of these complexes. Notably, the O-binding modes observed in the four wt and mutant structures held up exceedingly well even with the variation in H-bonding capacities. These wt and mutant Mb(ONO) compounds can be reduced with sodium dithionite to their respective nitrosyl Mb(NO) products. Verification of the formation of the nitrosyl Fe-NO derivative, and not the closely related nitroxyl Fe-HNO, was provided by FT-infrared spectroscopy. Arylhydrazines and derivatives are prevalent in nature and in pharmaceutical drugs. They interact with various heme proteins resulting in deactivation of the proteins. Eleven X-ray crystal structures of the products from the reactions of wt and mutant (H64A, H64Q, V68A/I107Y) Mbs with arylhydrazines (ArNHNH2; Ar = Ph, m-tol, and p-chlorophenyl) were obtained to 1.70-1.98 Å resolution. Direct Fe-carbon bonds were observed in all these derivatives, establishing that the hydrazine -NHNH2 moieties had been released from the reagents during their reactions with the Fe centers of the Mbs. Importantly, the C-atoms coordinating to the Fe centers were the same as those that bonded to the hydrazine functional groups, implying that the carbon-based radical intermediates were formed in close proximity to the Fe centers allowing for facile and efficient reactions to give the bioorganometallic Mb-aryl products. Significant distal pocket amino acid movements were observed in some cases with the larger p-chlorophenyl ligand aryl; for example, in the H64Q-chlorophenyl derivative, the Gln64 residue swings to a position outside the pocket towards the solvent region. We report the first expression, purification,… Advisors/Committee Members: Richter-Addo, George B. (advisor), West, Ann H. (committee member), Nicholas, Kenneth M. (committee member), Li, Jun (committee member), Ruyle, Jessica (committee member).

Subjects/Keywords: crystallography; myoglobin; nitrite; nitric oxide; nitroreductase; metronidazole

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wang, B. (2016). X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/34616

Chicago Manual of Style (16^th Edition):

Wang, Bing. “X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS.” 2016. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/34616.

MLA Handbook (7^th Edition):

Wang, Bing. “X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS.” 2016. Web. 25 Jan 2021.

Vancouver:

Wang B. X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS. [Internet] [Doctoral dissertation]. University of Oklahoma; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/34616.

Council of Science Editors:

Wang B. X-RAY CRYSTAL STRUCTURES AND CHARACTERIZATION OF THE PRODUCTS FROM THE INTERACTIONS OF MYOGLOBIN WITH NITROGEN OXIDES AND ARYLHYDRAZINES, AND NITROREDUCTASE INTERACTIONS WITH ORGANIC NITRO COMPOUNDS. [Doctoral Dissertation]. University of Oklahoma; 2016. Available from: http://hdl.handle.net/11244/34616

University of Oklahoma

4. Saeedi, Shahrokh. Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception.

Degree: PhD, 2015, University of Oklahoma

URL: http://hdl.handle.net/11244/23305

► Multi-band/multi-mode wireless communication systems have been receiving increased attention recently due to their potential for spectrum management in a dynamic spectral environment. Similarly radar systems,… (more)

▼ Multi-band/multi-mode wireless communication systems have been receiving increased attention recently due to their potential for spectrum management in a dynamic spectral environment. Similarly radar systems, which can operate in a variety of frequency bands, could provide significant flexibility in the operation for the future applications. However, multi-band/multi-mode operation adds to the complexity of the microwave systems. Reconfigurable RF/microwave components in general, and tunable filters in particular, have been shown to be promising in significantly reducing the system complexity. On the other hand, current trend of development in wireless communication and radar systems, forces more stringent requirements for electromagnetic spectrum sharing. Therefore, in many microwave applications a very high level of isolation between the channels are required. This is including simultaneous transmit-receive systems or co-site interference scenarios where the leakage from high power transmitter into receiver degrades the system performance. In these applications, conventional tunable bandpass/bandstop filters cannot provide enough isolation between transmitter and receiver. A promising solution which provides a tunable null, independent of the tunable transmission passband, is a dynamic-tunable bandpass-bandstop filter cascade. In this research, a frequency-agile bandpass-bandstop filter cascade for radar systems with simultaneous transmission and reception is designed to create advanced filtering functionality to isolate the desired signals from interfering signals in a spectrally-crowded environment. For a radar with simultaneous transmit and receive, two filter cascade will be required. Each filter will be used on a separate frequency agile transceiver but they will be synchronized to provide simultaneously a deep isolation region at one frequency for receive and a high power tolerant passband at an adjacent frequency for transmit. Advisors/Committee Members: Sigmarssion, Hjalti (advisor), Yeary, Mark (committee member), Hong, Yang (committee member), Ruyle, Jessica (committee member), Fulton, Caleb (committee member).

Subjects/Keywords: Microwave; Filter; Bandpass-Bandstop Cascade; Simultaneous Transmit and Receive

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Saeedi, S. (2015). Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/23305

Chicago Manual of Style (16^th Edition):

Saeedi, Shahrokh. “Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception.” 2015. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/23305.

MLA Handbook (7^th Edition):

Saeedi, Shahrokh. “Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception.” 2015. Web. 25 Jan 2021.

Vancouver:

Saeedi S. Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception. [Internet] [Doctoral dissertation]. University of Oklahoma; 2015. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/23305.

Council of Science Editors:

Saeedi S. Frequency-Agile Microwave Filters For Radars With Simultaneous Transmission and Reception. [Doctoral Dissertation]. University of Oklahoma; 2015. Available from: http://hdl.handle.net/11244/23305

University of Oklahoma

5. Winniford, Paul. Reconfigurable and multiband antennas with resonant and reactive loads.

Degree: PhD, 2020, University of Oklahoma

URL: http://hdl.handle.net/11244/326683

► Reactive and resonant loads have been used from the very beginning of antenna design to improve impedance matching, bandwidth, and current distributions on antennas, and… (more)

Subjects/Keywords: Antennas; Reconfigurable Antennas; Multifrequency Antennas; Loaded Antennas

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Winniford, P. (2020). Reconfigurable and multiband antennas with resonant and reactive loads. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/326683

Chicago Manual of Style (16^th Edition):

Winniford, Paul. “Reconfigurable and multiband antennas with resonant and reactive loads.” 2020. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/326683.

MLA Handbook (7^th Edition):

Winniford, Paul. “Reconfigurable and multiband antennas with resonant and reactive loads.” 2020. Web. 25 Jan 2021.

Vancouver:

Winniford P. Reconfigurable and multiband antennas with resonant and reactive loads. [Internet] [Doctoral dissertation]. University of Oklahoma; 2020. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/326683.

Council of Science Editors:

Winniford P. Reconfigurable and multiband antennas with resonant and reactive loads. [Doctoral Dissertation]. University of Oklahoma; 2020. Available from: http://hdl.handle.net/11244/326683

University of Oklahoma

6. Wang, Huiyu. Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes.

Degree: PhD, 2020, University of Oklahoma

URL: http://hdl.handle.net/11244/324967

► Electromagnetic-based energy harvesting materials and devices have emerged as a prominent research area in the last ten years, especially systems using ferrofluidic induction—a process that… (more)

▼ Electromagnetic-based energy harvesting materials and devices have emerged as a prominent research area in the last ten years, especially systems using ferrofluidic induction—a process that generates voltage via the pulsation of a ferrofluid (iron-based nanofluid) through a solenoid. This work includes the development of an analytical model and computational modeling methods to investigate ferrofluid pulsating flow within an energy harvesting device and the mass and heat transfer performance of a two-phase closed thermosyphon (TPCT) and oscillating heat pipe (OHP). First, an analytical model is proposed to predict the induced electromotive force (EMF) based on the flow behavior and magnetic properties of a pulsating ferrofluid energy harvesting device. The model identifies key parameters for describing and optimizing induction for ferrofluid pulsing through a solenoid. Data from a previously documented experimental study was used to validate the analytical model, and both the experimental data and analytical model show the same trends with the induced EMF increasing as a function of pulsating frequency and magnetic field strength as a higher percentage of the ferrofluid nanoparticle moments are aligned. Second, computational fluid dynamics (CFD) simulations were performed to predict the heat transfer performance of a TPCT. Simulations were performed using a three-dimensional finite-volume flow solver (ANSYS Fluent) with a pressure-based scheme for the solution of the continuity and momentum equations, volume-of-fluid method for resolution of the liquid-vapor phase interface, and a temperature-dependent model for interphase mass transfer by evaporation and condensation. Different model and numerical scheme combinations were investigated to identify an efficient and consistently accurate method using currently available software tools. To address issues with previously published simulation methods violating the conservation of mass, a new variable saturation temperature model was tested along with mass transfer coefficients based on the vapor-liquid density ratio and more physically realistic boundary conditions. The variable saturation temperature model significantly mitigated mass and energy imbalance in the simulations, for both constant heat flux and convection condenser boundary conditions. In addition, for the VOF discretization the Geo-Reconstruct scheme was found to be more accurate than the Compressive scheme available in Fluent without additional computational cost. Third, simulations of a vertical OHP were performed using the CFD methodology developed for the TPCT system. Results show simulations using appropriate values for the evaporation and condensation mass transfer time relaxation parameters and the new variable saturation temperature model are in good agreement with the available experimental data. For the OHP system, using the Compressive discretization scheme for the VOF model allowed for computationally efficient simulation. It is believed that the advances in analytical and computational modeling… Advisors/Committee Members: Walters, D. Keith (advisor), Walters, Keisha B. (advisor), Ruyle, Jessica E. (committee member), Shabgard, Hamidreza (committee member), Vedula, Prakash (committee member), Garg, Jivtesh (committee member).

Subjects/Keywords: Heat Transfer; Computational fluid dynamics (CFD); Electrodynamic energy harvesting

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Wang, H. (2020). Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/324967

Chicago Manual of Style (16^th Edition):

Wang, Huiyu. “Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes.” 2020. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/324967.

MLA Handbook (7^th Edition):

Wang, Huiyu. “Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes.” 2020. Web. 25 Jan 2021.

Vancouver:

Wang H. Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes. [Internet] [Doctoral dissertation]. University of Oklahoma; 2020. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/324967.

Council of Science Editors:

Wang H. Analytical and computational modeling of multiphase flow in ferrofluid charged oscillating heat pipes. [Doctoral Dissertation]. University of Oklahoma; 2020. Available from: http://hdl.handle.net/11244/324967

7. Pan, Yu. Analysis and Design of Reflectarray Antennas for Radar System Applications.

Degree: PhD, 2014, University of Oklahoma

URL: http://hdl.handle.net/11244/10489

► In recent years reflectarray has received more and more attention and it has been considered as a suitable candidate to replace the traditional reflectors due… (more)

▼ In recent years reflectarray has received more and more attention and it has been considered as a suitable candidate to replace the traditional reflectors due to its high-gain, low profile and low cost features. Reflectarray also eliminates the lossy feed network and costly transmitting and receiving modules when comparing with phased array antenna. It is desired to implement these functionalities with simple and effective techniques. Narrow bandwidth is the main issue which restricts the applications of the microstrip antennas, including the microstrip reflectarray. A broadband singlelayer reflectarray is introduced as the solutions to the issue of narrow bandwidth. A combination of two types of element configurations, including (i) ring elements and (ii) circular patch elements with ring boundary, enlarges the reflection phase range to more than 360◦ and thus enables the broadband operation of reflectarray. Blockage effect is another issue with the center-fed reflectarray. Certain obstacles, such as the feed horn, subreflector, and their supports, exist in reflectarray antennas. When these obstacles are in front of the reflectarray, the reflected wave is blocked, and the feed’s absorption also weakens the reflected power. An accurate prediction of this blockage effect in reflectarray design is essential. Five modeling schemes to account for the blockage effects in a reflectarray are described and also compared in terms of simulation time and consumed computing resource. In addition, another reflectarray with mainbeam direction steered 18◦ off broadside is also introduced to mitigate the blockage effect. Low cross-polarization performance is required for some reflectarray applications. For example, in dual-polarized weather radar the precipitation detection relies on complete isolation of orthogonal components of the fields, and thus negligible levels of cross-polarized radiation along the beam axis need to be maintained. A reflectarray design with suppressed cross-polarization is introduced in this dissertation. The directions of the surface currents can be changed by cutting gaps on the double-ring elements, so that the co-polar components of the surface currents enhance each other while the cross-polar components cancel each other, and thus a low cross-polarization level can be achieved. An X/Ku dual-band microstrip reflectarray with cosecant squared shaped beams has also been developed. The two operation frequency bands, 10 GHz and 15 GHz, are very close to each other. Thus the radiation interference between the two bands is taken into consideration and design is optimized to suppress the interference as much as possible. A dual-layer structure with cross-dipoles on the top layer and double-rings on the lower layer is adopted to suppress the interband couplings. Moreover, the dual-band elements are arranged in an interleaved manner in order to minimize element blockage. In addition, a phase-only synthesis technique is also introduced to obtain the two cosecant squared shaped … Advisors/Committee Members: Zhang, Yan (advisor), Lakshmivarahan, S. (committee member), Palmer, Robert (committee member), Zhang, Guifu (committee member), Ruyle, Jessica (committee member).

Subjects/Keywords: Engineering; Electronics and Electrical.

…x28;CPPAR) developed by the Advanced Radar Research Center of the University of… …Oklahoma [47–51]. CPPAR is a small-scale proof of concept 12 demonstrator capable of…

10 more images…

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Pan, Y. (2014). Analysis and Design of Reflectarray Antennas for Radar System Applications. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/10489

Chicago Manual of Style (16^th Edition):

Pan, Yu. “Analysis and Design of Reflectarray Antennas for Radar System Applications.” 2014. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/10489.

MLA Handbook (7^th Edition):

Pan, Yu. “Analysis and Design of Reflectarray Antennas for Radar System Applications.” 2014. Web. 25 Jan 2021.

Vancouver:

Pan Y. Analysis and Design of Reflectarray Antennas for Radar System Applications. [Internet] [Doctoral dissertation]. University of Oklahoma; 2014. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/10489.

Council of Science Editors:

Pan Y. Analysis and Design of Reflectarray Antennas for Radar System Applications. [Doctoral Dissertation]. University of Oklahoma; 2014. Available from: http://hdl.handle.net/11244/10489

8. Ye, Hao. Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices.

Degree: PhD, 2016, University of Oklahoma

URL: http://hdl.handle.net/11244/34898

► The interband cascade (IC) family of devices has been extended beyond mid-infrared lasers to include photovoltaic (PV) and photodetector (PD) devices. These devices utilize the… (more)

▼ The interband cascade (IC) family of devices has been extended beyond mid-infrared lasers to include photovoltaic (PV) and photodetector (PD) devices. These devices utilize the transition between conduction and valence bands for photon emission or absorption in the infrared region. The cascade structure recycles electrons to generate or collect multiple photons per electron. Epitaxial growths of the device structures are challenging because they consist of hundreds of quantum wells and require atomic layer precision in thickness control. Molecular beam epitaxy (MBE) was used to grow these structures with InAs, GaSb, AlSb, and their alloys on InAs or GaSb substrates. IC laser structures with InAs plasmon cladding layers were grown on InAs substrates for wavelengths greater than 3 μm. To provide a smooth initial surface for the cascade region, the optimal conditions for growth of homoepitaxial InAs layers were investigated over a wide range of substrate temperatures and As2/In flux ratios at a growth rate of 0.66 monolayer/s (ML/s). Material quality was investigated using differential interference contrast microscopy, scanning electron microscopy, and atomic force microscopy. The geometry of oval hillock defects on the InAs layers suggested that these defects originated at the substrate surface. The InAs-based IC lasers had emission wavelengths out to 11 μm, which is the longest wavelength among interband lasers based on III–V materials. By introducing intermediate superlattice (SL) cladding layers to enhance optical confinement and reduce internal absorption loss, the first continuous wave operation of InAs-based IC lasers at room temperature was demonstrated. The threshold current density of 247 A/cm2 for emission near 4.6 μm is the lowest ever reported among semiconductor mid-infrared lasers at similar wavelengths. ICPV and ICPD devices were developed based on the architecture of IC lasers. They both consist of multiple discrete InAs/GaSb SL absorbers sandwiched between electron and hole barriers. ICPV devices can be used in thermophotovoltaic systems that convert radiant energy from a heat source into electricity. Strain-balanced InAs/GaSb SL structures were achieved by adjusting the group-V overpressure during MBE growth. Two- and three-stage ICPV devices operated at room temperature with substantial open-circuit voltages at a cutoff wavelength of 5.3 μm, the longest ever reported for room-temperature PV devices. The interfaces of InAs/GaSb SLs were studied with the goal of improving the PDs designed for the long-wavelength infrared region. Two ICPD structures with different SL interfaces were grown by MBE, one with a ~1.2 ML-thick InSb layer inserted intentionally only at the GaSb-on-InAs interfaces and another with a ~0.6 ML-thick InSb layer inserted at both InAs-on-GaSb and GaSb-on-InAs interfaces. The material quality of the PD structures was similar according to differential interference contrast microscopy, atomic force microscopy, and x-ray diffraction measurements. The device performances were not… Advisors/Committee Members: Yang, Rui (advisor), Santos, Michael (advisor), Murphy, Sheena (committee member), Ruyle, Jessica (committee member), Shi, Zhisheng (committee member), Johnson, Matthew (committee member).

Subjects/Keywords: Molecular Beam Epitaxy; III-V Semiconductor Material; Laser; Detector

…at the University of Oklahoma [24]. There are several advantages of using the…

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APA (6^th Edition):

Ye, H. (2016). Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices. (Doctoral Dissertation). University of Oklahoma. Retrieved from http://hdl.handle.net/11244/34898

Chicago Manual of Style (16^th Edition):

Ye, Hao. “Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices.” 2016. Doctoral Dissertation, University of Oklahoma. Accessed January 25, 2021. http://hdl.handle.net/11244/34898.

MLA Handbook (7^th Edition):

Ye, Hao. “Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices.” 2016. Web. 25 Jan 2021.

Vancouver:

Ye H. Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices. [Internet] [Doctoral dissertation]. University of Oklahoma; 2016. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/11244/34898.

Council of Science Editors:

Ye H. Molecular Beam Epitaxy of InAs, GaSb, AlSb Structures for Interband Cascade Devices. [Doctoral Dissertation]. University of Oklahoma; 2016. Available from: http://hdl.handle.net/11244/34898

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