Shielded microstrip subarray with large bandwidth and low cross polarization

Two subarrays of four elements have been investigated for possible use in a satellite-borne antenna requiring good cross polarisation performance in the broadside direction. The bottom and sides of the antennas are shielded. Shielding involves replacing the microstrip feed line by a stripline, and then isolating the antenna with lateral shielding. Parasitic resonances which appear in the enclosed feeding structures are eliminated with shorting pins. Both subarrays exhibit almost the same performance, except a better standing wave ratio is observed for the double-patch subarray in the middle of the bandwidth. The major advantage of the latter is the small number of shorting pins used, which permits the realization of more complex feed structures if necessary. The radiation pattern of the single-patch subarray is a little more symmetrical than that of the double-patch subarray; this difference can be attributed to misalignment. Subarrays of this type are suitable for direct integration. They are totally independent and a variety of antennas can be built by associating the desired number of subarrays.<>