A two-ring circular phased-array antenna for mobile satellite communications

This paper presents the design and development of an L-band planar, multi-layer circular array for possible use with the Australian geostationary mobile-satellite-communications system, Mobilesat/sup TM/. Twelve single-feed, stacked aperture-coupled microstrip patches, interleaved with low-cost dielectric foam and arranged in two rings, form the array. The beam-forming network is comprised of three-bit phase shifters, which are located under the antenna elements. Low-cost UHF-band switching diodes were used to minimize the developmental cost of these phase shifters. In order to make the diodes operational at L-band, an LC compensation technique was applied to the diodes to tune out parasitic reactance. Experimental results for individual antenna elements and phase shifters, followed by the results for the entire array, are presented. The indoor testing results for the manufactured antenna showed that the array satisfies the specifications of Mobilesat/sup TM/. This was also confirmed by outdoor field trials with a NEC S1 transceiver terminal.