C.-I. Hung

Synthesis of array antenna with broad nulls

A technique is presented for synthesizing a linear phased array antenna pattern with prescribed broad null by controlling phase only. The problem of array pattern synthesis is formulated as interference-signal-ratio (ISR) minimization problem. Numerical technique based on steep descent iterative procedure is used for an optimum reduction. Numerical and experimental results are presented to illustrate the performance achievable.<<ETX>>

Sidelobes cancellation in an offset reflector antenna system using a linear phased array feed

A pattern synthesis of an offset reflector antenna system using a five-bit phase-only controlled linear phased array feed is presented. Experimental results indicate this configuration can enhance the performance of an offset reflector antenna system in both polluted microwave and surface distortion environments. The implementation of a linear phased array feed in an offset reflector antenna system not only ameliorates reflector surface distortion, but also rejects jammers out of the antenna system by adjusting nulls to jammer directions. With this configuration, the reflector antenna system also has a larger scan angle than a traditional single feed reflector antenna system.<<ETX>>

The development of a compact point-defense phased array antenna

The design and construction of an S-band space-fed phased array antenna are presented. The antenna is a major unit of the MARS (Meliorated Advanced Radar System), an S-band, space-fed phased array, multifunction, mobile radar system designed for pointing defense. A prototype scaled-down MARS space-fed array antenna was designed an built with 254 radiation elements. The crucial objective of this program was to demonstrate the feasibility of producing a low-cost, high-performance, easy-to-maintain, electronically phased array antenna. The critical components have been well developed and tested.<<ETX>>

Dual-band slot antenna design with a thin cavity

A design of dual-band cavity-backed slot antenna is presented for GPS and S-band radar applications. In the design, a very thin cavity (0.017 λ0 in thickness at 1.575 GHz) is used to achieve unidirectional radiation. The dual-band responses of the antenna are excited by the slot resonance at 1.575 GHz and waveguide transition effect at 2.4 GHz. Even with very small cavity thickness, reasonable impedance bandwidths are obtained as 1.6% (26 MHz) at 1.575 GHz and 8.4% (203 MHz) at 2.4 GHz. The proposed slot can also be loaded with a spurline to adjust the antenna centre frequency and the phase of the radiated field. All designs in this paper have been validated with experiments. Satisfactory results have been obtained.

Compact antenna design with bandwidth enhancement

A novel wideband compact antenna design at the edge of the ground plane is presented. The design, mainly composed of an edge-coupled capacitor as a tuning mechanism, can be used as building blocks for future multi-band antennas with reconfigurable operation in which the capacitor is replaced by a varactor. The antenna is first designed with an inductive feed. The corresponding equivalent circuit is also presented, in which the contribution of each parts of the antenna are explained. The antenna can be miniaturized by tuning the edge-coupled capacitor and the inductive effect between the antenna structure and the ground plane. The capacitive feed mechanism is later introduced to replace the original inductive feed. With the capacitive feed, the impedance bandwidth of the antenna can be significantly enhanced from 9% (2.15-2.41 GHz) to 49.6% (1.695-2.763 GHz), while the size of the antenna is 10×11 mm2.

A simple approach to generate concomitant broad beam for the advanced phased array antenna

The authors present the application of quadratic-phase weights to produce concomitant broad beam with the same aperture of the pencil-beam phased array antenna. The concomitant broad beam is applied to improve the efficiency of the missile acquisition before the missile midcourse during radar engagement situation. The major objective is to find optimal procedure to evaluate the influence of the beamwidth and power gain for the existing antenna pattern. The procedure is verified on both corporate and space fed pencil-beam phase array antenna with three channels (SUM/AZ/EL) pattern.<<ETX>>

An introduction to a S-band compact space-fed phased array antenna

A low-cost, high-performance, facile-maintenance, compact point-defense phased array antenna is presented. The scaled down MARS (meliorated advanced radar system) antenna, 254 elements for each aperture, is designed and built with 12% bandwidth in S-band. The high-performance OEM (open-ended microstrip) rectangular waveguide type radiator with 5-b ferrite phase shifter is used as the aperture element. A compact multimode feed horn is fabricated to satisfy the desired radiation field pattern of the scaled down MARS antenna. The physical antenna system construction and sub-system test results are given.<<ETX>>