M.-Y. Li

Development of a retrodirective wireless microwave power transmission system

This paper describes the design of a small-scale system for demonstrating retrodirective wireless power transmission. A solid-state phased array transmitter with retrodirective control drives two 5.8 GHz circular-polarized (CP) transmit antenna subarrays that illuminate a remote CP rectenna array. The total power transmitted is about 40 W. A 2.9 GHz pilot beam projected from the rectenna site is received at the transmit site and processed for retrodirective control of the 5.8 GHz transmitter.

High power four-way power divider/combiner

A four-way waveguide power divider/combiner has been developed using a radial waveguide. The divider has an insertion loss of less than 0.5 dB and a power balance of +or-0.2 dB over a bandwidth of 2.5 GHz at X-band. A power combiner using this circuit and four Gunn oscillators has been demonstrated with over 70% combining efficiency. The circuit should have applications in millimeter-wave power combining and high-power microwave systems.<<ETX>>

Theoretical and experimental study of the input impedance of the cylindrical cavity-backed rectangular slot antennas

The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length. >

A novel millimeter-wave beam-steering technique using a dielectric-image-line-fed grating film

This paper introduces a novel, broadband, low-cost technique for beam steering at millimeter-wave frequencies using a moveable grating film fed by a dielectric image line. An excellent radiation pattern is maintained across the measured scanning ranges at 30, 35, and 40 GHz, with up to 53/spl deg/ scanning reported at 35 GHz. Theoretical calculations closely predict the observed scan angle across the entire range of measurement.

Narrowband filter and annular slot antenna for PCS applications

A new narrowband filter has been developed for PCS applications. This filter has a 0.2 dB passband ripple bandwidth of 0.568% and is 60% smaller than the normal parallel coupled design. The filter can be integrated with the microstrip feedline of a novel annular slot antenna (ASA). The ASA has a 4.5% bandwidth and a planar structure. This antenna can be conveniently located on the chassis of a mobile PCS unit.

Slot antennas fed by circular waveguides

Slot antennas fed by a circular waveguide or a cylindrical cavity have been developed. The slot antennas can be rectangular slots or cross slots. Radiation patterns have been measured for both slot configurations. The use of circular waveguides has many advantages, such as a symmetrical feeding arrangement and the realization of cross polarization feeding.<<ETX>>

Simplified analysis of aperture coupled microstrip antenna fed by dielectric image line

The paper presents a simplified analysis of aperture coupled microstrip antenna fed by a dielectric image line. The cavity model is used to represent the fields in the microstrip antenna. The dielectric image line is assumed to be propagating only the fundamental mode. The magnetic current source due to the electric field in the aperture is assumed to be a half-sine wave. The image line is terminated by a matched load. The total impedance of the antenna and the matched load seen at the reference plane in the image line is calculated and validated with experimental results.

Input impedance of the slot antennas backed by cylindrical cavity

The input impedance of a cylindrical cavity-backed slot antenna has been derived based on the mode matching method and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. Numerical results agree very well with measurements. It is pointed out that the results should have many applications in conformal antennas and arrays.<<ETX>>