James Sor

Miniature low-loss CPW periodic structures for filter applications

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.

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

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

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 structures 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.

Multi-mode microstrip antennas for reconfigurable aperture

A multi-mode reconfigurable antenna structure is explored. The unique phased array system utilizes three different microstrip antennas: the quasi-Yagi endfire antenna for wideband endfire coverage, patch antennas for moderate gain at broadside, and high gain frequency scanned leaky-wave antennas. The aperture configuration can be controlled through a combination of DSP and MEMS switches. The proposed structure exhibits good isolation between the different aperture ports. The radiation patterns in each reconfigured mode of operation do not show any noticeable degradation.

A broadband uniplanar quasi-Yagi active array for power combining

An active array with a quasi-Yagi antenna element is presented. The array has a bandwidth of 60% (VSWR <2) and a fan-beam pattern. The gain of the active array is measured to range from 22-25 dB from 8-11.7 GHz. The single layer compact design makes this array antenna ideal as a building block in larger 2-D arrays.

A broadband 64-element 2-D quasi-Yagi antenna array

A 2-D antenna array using a planar quasi-Yagi antenna element is presented. The X-band array prototype has a broad bandwidth of 40% (YSWR<2). Measured radiation patterns show a well defined end-fire main beam with 3-dB beamwidth of 12/spl deg/ at 9 GHz and gain ranging between 20 to 13.6 dB across the entire operating band.

A Broadband Quasi-Yagi Antenna Array

A broadband quasi-Yagi X-Band antenna array with a fanbeam-pattern is presented. The bandwidth of the array (VSWR < 2.0) is found to be 50% and a measured gain of 10-12 dB is measured in the operating range. An array with a 12° beam tilt is also presented. The endfire array demonstrates a front-to-back ratio better than 20 dB and cross-polarization better than ¿15 dB in the operating band. The fanbeam pattern is useful for mobile communications applications. Active 2-D arrays based on this concept should prove useful for radar, communications and quasi-optical power combining applications.

Reconfigurable quasi-fractal transmission line structures

Several transmission line structures bearing fractal-like characteristics are presented. Using pin-diode switches, the transmission line structures can be reconfigured into quasi-fractal self-similar structures. The reconfigured structures closely resemble the pre-reconfigured transmission line structures both physically and electromagnetically, with the frequency response inversely proportional to the number of segments involved. Proposed quasi-fractal transmission fine structures for both microstrip and coplanar waveguide are presented and biasing issues are discussed.