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:(Grating lobe). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


University of Oklahoma

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

Degree: PhD, 2019, University of Oklahoma

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

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th 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 (16th Edition):

Bhowmik, Lal Mohan. “Applications of Floquet Analysis to Modern Phased Array Antennas.” 2019. Doctoral Dissertation, University of Oklahoma. Accessed February 27, 2021. http://hdl.handle.net/11244/321405.

MLA Handbook (7th Edition):

Bhowmik, Lal Mohan. “Applications of Floquet Analysis to Modern Phased Array Antennas.” 2019. Web. 27 Feb 2021.

Vancouver:

Bhowmik LM. Applications of Floquet Analysis to Modern Phased Array Antennas. [Internet] [Doctoral dissertation]. University of Oklahoma; 2019. [cited 2021 Feb 27]. 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


Penn State University

2. Anderson, Brian Eric. GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES .

Degree: 2008, Penn State University

The effect of placing a structural acoustic filter between the water medium and the transducer elements of an array is investigated, in this thesis, to help reduce undesirable grating lobes. A plate is mounted to transducer elements with a thin decoupling polyurethane layer between the transducers and the plate. The plate acts as a radiation/incidence angle filter to pass energy at angles near normal incidence, but suppress energy at large incidence angles. The plate must possess a very high bending stiffness while maintaining low mass to achieve optimal results. Grating lobe reduction is achieved at the expense of limiting the available steering of the main lobe. Within this steer angle limit the main lobe beams can be steered as normal while the grating lobe level is reduced by the plate’s angular filtering. The insertion of a plate structural filter provides an inexpensive and easily implemented approach to extend usable frequency bandwidth with reduced level grating lobes, without increasing the number of array elements. Even though some data matches theory well, a practical material has yet to be found that possesses optimal material properties. To the author’s knowledge, this thesis represents the first attempt to advantageously utilize a plate to provide angular dependent sound transmission filtering above the plate’s critical frequency (the supercritical frequency region). Theoretical analysis, numerical analysis, and extensive experimental results have been performed and a comparison will be presented in this thesis. The angular dependence of sound transmission through a plate is reviewed, followed by design considerations to optimize a plate for angular filtering. The optimal thickness for a plate depends on the plate’s material properties. Equivalent circuit modeling and finite element modeling was applied, and is compared to. Extensive experimental results conducted with bars and a plate will be shown. Good agreement with theory and modeling is achieved for an alumina bar bonded to transducer elements. Advisors/Committee Members: William Jack Hughes, Committee Chair/Co-Chair, Courtney Brice Burroughs, Committee Member, Stephen A Hambric, Committee Member, Nadine Barrie Smith, Committee Member.

Subjects/Keywords: grating lobe; array; transducer; transducer array; supercritical; coincidence; plate; structural acoustics

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Anderson, B. E. (2008). GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES . (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/7292

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):

Anderson, Brian Eric. “GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES .” 2008. Thesis, Penn State University. Accessed February 27, 2021. https://submit-etda.libraries.psu.edu/catalog/7292.

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

MLA Handbook (7th Edition):

Anderson, Brian Eric. “GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES .” 2008. Web. 27 Feb 2021.

Vancouver:

Anderson BE. GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES . [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Feb 27]. Available from: https://submit-etda.libraries.psu.edu/catalog/7292.

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

Council of Science Editors:

Anderson BE. GRATING LOBE REDUCTION IN TRANSDUCER ARRAYS THROUGH STRUCTURAL FILTERING OF SUPERCRITICAL PLATES . [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/7292

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

.