Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(infinite array). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


Penn State University

1. Gregory, Micah Dennis. Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment .

Degree: 2009, Penn State University

In recent years there has been much research into increasing the operating bandwidth of radio frequency systems. The need for wideband systems arise through demand for high data rate communications, multi-frequency radars, and other multipurpose communications devices. In addition to the circuitry of such systems, the antenna is an important component as well for energy to be effectively radiated over large operating bandwidths. Many designs and optimizations have focused on creating wideband antennas operating in isolation, but arrays are attractive because of the electronic beam steering capabilities and high gain properties that they exhibit. This thesis covers two aspects of wideband antenna array design. The first topic is the arrangement of antenna elements in an array to maintain low relative sidelobe levels over a wide bandwidth. The most common configuration, the periodic array, generates grating lobes when the elements are electrically far apart. Grating lobes are portions of the array factor with power equal to the main beam; they cause energy transmission in undesired directions. Arranging the elements in an aperiodic fashion often has the benefit of reducing sidelobe levels over extended bandwidths if designed properly. The method used for aperiodically arranging elements is important to realize arrays with sufficient sidelobe suppression over a useful bandwidth. The recently introduced polyfractal array design approach is one successful method. Using the recursive nature of fractals and a powerful optimization technique, arrays exhibiting ultra-wideband performance with very low sidelobe levels have been created. The focus of the work presented here is to validate the effectiveness of polyfractal arrays consisting of real antenna elements. To this end, two small polyfractal arrays have been optimized, fabricated, and examined for wideband performance. The second topic is the optimization of elements that are arranged in an infinite planar periodic structure. Arranging elements periodically allows easy of manufacturing and implementation. Although the upper frequency of operation is limited by the occurrence of grating lobes, large bandwidth percentages can be had if the antenna element is designed properly. Often, antenna arrays are created by designing a single element and placing it in an array configuration, though this comes with certain consequences. For instance, the antennas can shift their resonant frequencies and input return loss can become poor because of mutual coupling between elements. In addition, performance can become severely degraded when arrays are scanned, especially close to grazing angles. For these reasons, it becomes advantageous to design and optimize the antenna elements while they are in an array. In this manner, any effects due to nearby elements are automatically accounted for. Specialized simulation software along with a genetic algorithm is used for this purpose, creating effective wideband radiating elements to be used in planar microstrip phased… Advisors/Committee Members: Douglas Henry Werner, Thesis Advisor/Co-Advisor, Pingjuan Li Werner, Thesis Advisor/Co-Advisor, Douglas Henry Werner, Dissertation Advisor/Co-Advisor.

Subjects/Keywords: polyfractal; antenna array; genetic algorithm; array factor; periodic array; planar array; infinite array; microstrip antenna

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Gregory, M. D. (2009). Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/10456

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Gregory, Micah Dennis. “Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment .” 2009. Thesis, Penn State University. Accessed May 06, 2021. https://submit-etda.libraries.psu.edu/catalog/10456.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Gregory, Micah Dennis. “Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment .” 2009. Web. 06 May 2021.

Vancouver:

Gregory MD. Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment . [Internet] [Thesis]. Penn State University; 2009. [cited 2021 May 06]. Available from: https://submit-etda.libraries.psu.edu/catalog/10456.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Gregory MD. Validation of Linear Polyfractal Arrays and the Optimization of Antenna Elements in an Infinite Array Environment . [Thesis]. Penn State University; 2009. Available from: https://submit-etda.libraries.psu.edu/catalog/10456

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Southern California

2. Ghaemi Oskouei, Babak. Stability of body-vortex systems: Application to aquatic locomotion.

Degree: PhD, Aerospace & Mechanical Engineering (Dynamics & Control), 2013, University of Southern California

Mathematical modeling and analysis of biological systems such as swimming and flying is an interdisciplinary research field with an extensive range of applications including the design of unmanned underwater robots and swarm of robots that swim together in a coordinated way similar to schooling fish. One of the main objectives of our work is to develop mathematical models for certain aspect of schooling. In particular, we examine (1) the interaction of a single fish with ambient vorticity possibly generated by other neighboring fish; and (2) the interaction of multiple fish wakes in large fish schools.; For the first part, we propose a reduced model of a rigid body interacting with point vortices in potential fluid and demonstrate that the rigid body can swim upstream in the direction opposite to the motion of point vortices at no energy cost. Indeed, the rigid body itself does not generate any force and its motion is due entirely to the energy exploited from the presence of the point vortices. We comment on the stability of these motions and propose under-actuated active control methods to achieve locomotion in unsteady wakes.; In the second part, we consider the interaction of multiple reverse von K´arm´an vortex streets as a model of the mid-wake region of large fish schools. We focus on the wake dynamics to gain insight into the role of the fluid in transporting oxygen and nutrients to inner fish as well as its role in facilitating or acting as flow barriers to passive locomotion.; We examine the topology of the streamline patterns in a frame moving with the same translational velocity as the streets which lends insight into fluid transport through the mid-wake region. Advisors/Committee Members: Kanso, Eva (Committee Chair), Newton, Paul K. (Committee Member), Redekopp, Larry G. (Committee Member), Mitra, Urbashi (Committee Member).

Subjects/Keywords: point vortex; dynamical systems; stability analysis; vortex wake; fish; fish schooling; solid body; fluid; interaction; floquet theory; inviscid; incompressible; irrotational flow; 2D flow; ellipse; circle; Kirchhoff Routh; classical; Milne Thomson; circle theorem; complex potential; velocity; kinematics; submerged; Grobli; periodic; thrust; drag; von Karman; street; mid wake; streamline; pattern; topology; time scale; bifurcation; Doubly-Infinite Array; zeta function; vortex lattice; orientation control; elongated body; staggered street; symmetric street; convergence; integral test; dynamics; control; ideal fluid; aquatic locomotion; propulsion

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Ghaemi Oskouei, B. (2013). Stability of body-vortex systems: Application to aquatic locomotion. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029

Chicago Manual of Style (16th Edition):

Ghaemi Oskouei, Babak. “Stability of body-vortex systems: Application to aquatic locomotion.” 2013. Doctoral Dissertation, University of Southern California. Accessed May 06, 2021. http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029.

MLA Handbook (7th Edition):

Ghaemi Oskouei, Babak. “Stability of body-vortex systems: Application to aquatic locomotion.” 2013. Web. 06 May 2021.

Vancouver:

Ghaemi Oskouei B. Stability of body-vortex systems: Application to aquatic locomotion. [Internet] [Doctoral dissertation]. University of Southern California; 2013. [cited 2021 May 06]. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029.

Council of Science Editors:

Ghaemi Oskouei B. Stability of body-vortex systems: Application to aquatic locomotion. [Doctoral Dissertation]. University of Southern California; 2013. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/451808/rec/6029

.