Hassan Chreim

Multifeed EBG dual Band Antenna for Spatial Mission

We present the design of a multibeam reflector antenna fed by a multifeed dual-band electromagnetic band gap (EBG) antenna to achieve a high-gain multispot coverage for space applications. First, we design a dual-band EBG antenna in monofeed configuration. This antenna is composed of double-layer frequency selective surfaces (FSSs) arranged in the longitudinal direction and a square horn as a feed. Then, the same antenna in multifeed configuration is studied, and the results are compared to those obtained in monofeed configuration in order to emphasize the problem of coupling, generally encountered in multifeed configuration. Consequently, filters are used in order to reduce the parasitic interferences and obtain good radiation characteristics. As shown in this paper, the same EBG phase center is obtained in both frequency bands. Finally, we have studied the whole system composed of the offset reflector and the multifeed EBG dual-band antenna. An edge of coverage (EOC) gain higher than 42 dBi and sidelobes levels lower than −18 dBi are obtained over all spots.

A simplified methodology for matched filter design with constraints - filter-antenna subsystem for space application

A new simplified methodology for the design of microwave cavity filters has been presented. The presented work is based on the optimization of Belevitch polynomials and inspired from the Simplified Real Frequency Technique (SRFT). One can bypass the use of computationally expensive circuit simulation softwares which are used to optimize the lumped element circuit model of the cavity filters. The procedure is applied for the design of filters for a multi-feed filter-antenna subsystem for space application.

Circularly polarized EBG antenna using meander lines polarizer as a reflector focal feed for Ka-band space applications

This article presents a first step towards the design of a multi-feed circularly polarized EBG antenna which serves as a reflector focal array. The circular polarization is obtained by using a multilayer meander lines polarizer, placed above a linearly polarized EBG antenna. The details of the antenna and the polarizer are given and the “transparent” effect of the polarizer on the antenna feed performance is emphasized after comparing the performance with and without the polarizer. The designed antenna is used to illuminate a reflector antenna for RX Ka-band space applications [29.5 - 30] GHz, and the coverage performance will be shown.

Cylindrical array of EBG sectoral antennas for Radar applications

This paper presents an additional work on a previous EBG cylindrical antenna in order to conceive a steerable antenna for Radar applications which require the coverage of the horizontal plane with a high gain (higher than 25 dB). The already designed antenna provides 18 beams with 15 dBi of maximum directivity. That is why some modifications were applied on it in order to obtain more beams in the horizontal plane (30 beams) and increase its gain. Moreover, the theories of cylindrical arrays in the horizontal plane and the multi-feed in the vertical plane are used which allows further gain improvement and reaching the required one.