J. Sor

Bio: J. Sor is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Microstrip antenna & Coplanar waveguide. The author has an hindex of 5, co-authored 7 publications receiving 655 citations.

A new quasi-Yagi antenna for planar active antenna arrays

Abstract: In this paper, a novel broadband planar antenna based on the classic Yagi-Uda dipole antenna is presented, and its usefulness as an array antenna is explored. This "quasi-Yagi" antenna is realized on a high dielectric-constant substrate, and is completely compatible with microstrip circuitry and solid-state devices. This antenna achieves a measured 48% frequency bandwidth for voltage standing-wave ratio <2, better than a 12-dB front-to-back ratio, smaller than -15 dB cross polarization, and 3-5-dBi absolute gain. Mutual coupling of the antenna in an array environment is investigated. Finally, three simple arrays are presented, demonstrating the usefulness of the antenna as an array element. This novel antenna should find wide application in wireless communication systems, power combining, phased arrays, and active arrays, as well as millimeter-wave imaging arrays.

Miniature low-loss CPW periodic structures for filter applications

Abstract: Several novel periodic structures for coplanar waveguides are presented. The proposed structures exhibit low insertion loss in the passband, simple fabrication, and slow-wave characteristics. These structures are applied to realize miniature low-pass filters one-tenth the size of conventional filters, with spurious-free response and deep attenuation levels using only three cells.

Coplanar waveguide fed quasi-Yagi antenna

Abstract: A novel coplanar waveguide fed quasi-Yagi antenna is presented. A wide bandwidth is achieved by using a broadband coplanar waveguide to a slotline balun. An X-band prototype has been realised which demonstrates a broad bandwidth (30%), –19 dB front-to-back ratio, and cross-polarisation better than -17 dB at 10 GHz.

A novel low-loss slow-wave CPW periodic structure for filter applications

Abstract: A novel periodic slow-wave structure for CPW is presented. This proposed structure exhibits low insertion loss in the passband, simple fabrication, and is intrinsically matched. The structure is applied to realize a miniature lowpass filter one-tenth the size of conventional filters, with spurious-free response and deep attenuation levels using only three cells.

A reconfigurable leaky-wave/patch microstrip aperture for phased-array applications

Abstract: A novel reconfigurable leaky-wave/patch microstrip aperture is introduced and characterized. The structure consists of a long leaky-wave microstrip antenna that has been segmented into several smaller patch antennas. The multimode structure can be reconfigured into a patch antenna anywhere along the aperture of the leaky-wave antenna with two degrees of freedom. p-i-n-diode switches are utilized to switch between the different aperture configurations. The structure's unique field profile is utilized to minimize insertion loss in the leaky-wave mode and also to maximize isolation between the different aperture ports. Radiation patterns demonstrate excellent radiation characteristics consistent with standard leaky-wave and patch-antenna patterns. The reconfigurable leaky-wave/patch concept is applied to realize some unique multimode array configurations offering wide scan coverage and enhanced flexibility over traditional phased-array systems.

Epitaxial growth of transparent p-type conducting CuGaO2 thin films on sapphire (001) substrates by pulsed laser deposition

Abstract: Transparent p-type conducting CuGaO2 thin films were prepared on α-Al2O3 (001) single-crystal substrates by pulsed laser deposition. The films were grown epitaxially on the substrates in an as-deposited state. X-ray pole figure analysis revealed that the films were composed of two types of epitaxial grains, both with c axes oriented perpendicular to the surface and a axes rotated 60° with respect to each other around the c axis. Observation of the CuGaO2 thin films by atomic force microscopy and high-resolution transmission electron microscopy substantiated this conclusion. The films have high optical transparency (∼80%) in the visible region, and the energy gap of CuGaO2 for direct allowed transition was estimated to be 3.6 eV. p-type conductivity was confirmed by Seebeck and Hall measurements. The electrical conductivity, carrier (positive hole) density, and Hall mobility of the films at room temperature were 6.3×10−2 S cm−1, 1.7×1018 cm−3, and 0.23 cm2 V−1 s−1, respectively.

Multi-beam antenna

Abstract: A plurality of antenna elements on a dielectric substrate are adapted to launch or receive electromagnetic waves in or from a direction substantially away from either a convex or concave edge of the dielectric substrate, wherein at least two of the antenna elements operate in different directions. Slotlines of tapered-slot endfire antennas in a first conductive layer of a first side of the dielectric substrate are coupled to microstrip lines of a second conductive layer on the second side of the dielectric substrate. A bi-conical reflector, conformal cylindrical dielectric lens, or discrete lens array improves the H-plane radiation pattern. Dipole or Yagi-Uda antenna elements on the conductive layer of the dielectric substrate can be used in cooperation with associated reflective elements, either alone or in combination with a corner-reflector of conductive plates attached to the conductive layers proximate to the endfire antenna elements.

Meta-element antenna and array

Abstract: An antenna having at least one main element and a plurality of parasitic elements. At least some of the elements have coupling elements or devices associated with them, the coupling elements or devices being tunable to thereby control the degree of coupling between adjacent elements. Controlling the degree of coupling allows a lobe associated with the antenna to be steered.

Integration of packaged RF MEMS switches with radiation pattern reconfigurable square spiral microstrip antennas

Abstract: This work describes the integration of commercially available packaged radio frequency microelectromechanical system (RF MEMS) switches with radiation pattern reconfigurable microstrip antennas. Most applications of RF MEMS switches consider the switches as only circuit elements. In contrast, the implementation of packaged switches in this particular antenna must address not only the simple open/closed behavior of the switches but also their impact on the radiation characteristics of the reconfigurable antenna. Here, two Radant MEMS single-pole single throw (SPST) SPST-RMSW100 (packaged RF MEMS) switches are used to reconfigure the radiation patterns of a resonant square spiral microstrip antenna between endfire and broadside over a common impedance bandwidth. Switch insertion, matching network design, and other issues are addressed. Results for both simulated and measured antennas, as well as recommendations for future work in this area, are provided.

III nitrides and UV detection

Abstract: III nitrides have become the most exciting challenge in optoelectronic materials in the last decade. Their intrinsic properties and an intense technological effort have made possible the fabrication of reliable and versatile detectors for short wavelengths. In this work, materials and devices issues are considered to provide a full picture of the advances in nitride UV photodetection. First, basic structures like photoconductors, Schottky, p-i-n and metal-semiconductor-metal photodiodes and phototransistors are compared, with emphasis on their specific properties and performance limitations. The efforts in the design and fabrication of more advanced detectors, in the search for higher quantum efficiency, contrast, signal-to-noise or speed operation, are reviewed afterwards. Metal-insulator-semiconductor diodes, avalanche photodetectors and GaN array detectors for UV imaging are also described. Further device optimization is linked with present materials issues, mainly due to the nitride quality, which is a direct result of the substrate used. The influence of substrates and dislocations on detector behaviour is discussed in detail. As an example of AlGaN photodetector applications, monitoring of the solar UV-B radiation to prevent erythema and skin cancer is presented.