Browsing by Author "Chou, Hai Cheng"

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Compact Mikaelian Lens Synthesized by Metasurfaces
(2018-03-01)
Yang, Jiun Wen
;
Lai, Wei Yu
;
Chou, Hai Cheng
;
Kehn, Malcolm Ng Mou
;
電機工程學系
Synthesized using metasurfaces, we propose the implementation of the rectangular Mikaelian lens, one that is not only just flat but now also thin, thus enabling impingent wavefronts to converge at focal points over shorter distances, a feature that no other contemporary types of circularly shaped lenses are able to achieve. The subsequent savings of space and weight afforded by this unique property could be invaluable. By further postprocessing of the fields extracted from the simulations, the degree of focusing attained by the lens is also quantitatively characterized, thus offering insights beyond mere visual inspection of field patterns. The phenomenon of power concentration has been successfully demonstrated with simulations that are well corroborated by results of measurements carried out on a manufactured prototype.
The Double-Focus Generalized Luneburg Lens Design and Synthesis Using Metasurfaces
(2018-09-01)
Chou, Hai Cheng
;
Tung, Nai-Lun
;
Kehn, Malcolm Ng Mou
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
In this communication, we study the use of metasurfaces comprising circular metallic patches printed on a grounded dielectric substrate to design and synthesize the double-focus generalized Luneburg lens (DF-GLL) at microwave frequencies. When illuminated by incident plane waves arriving from not just one but numerous azimuth angles, the simulated design displays two clear focal spots toward all directions, thereby exhibiting rotational symmetry which facilitates beam switching and scanning. How such circular patch elements compare with square ones is also investigated in terms of the range over which refractive indices can be synthesized as well as the bandwidths of both focal points produced by DF-GLLs composed of patches bearing those two shapes. When operated as a radiating antenna instead, for which excitation source feeds are placed at the two focal spots aligned along the azimuth angle pertaining to that intended beam direction, strong directivilies toward all directions are achieved as simulated radiation patterns show. A prototype of the design was also manufactured and measurement results agree well with predictions by simulations, particularly in terms of realizing two distinct focal points toward several azimuth directions.