Design of a planner ku band receive antenna array for mobile platforms

A wideband, planar and low profile antenna array is proposed and designed for Ku band direct broadcast from satellite reception for mobile systems. Contrary to earlier designs, the array antenna covers entire downlink Ku-band frequencies (10.8 - 12.75 GHz) for simultaneous reception from multiple transponders. In this thesis, we first propose figure-of-merits (FOMs) to classify antennas in terms of their performances. Among possible antenna configurations, we show that aperture coupled antennas exhibit superior performance when FOM based comparisons are made. Using this single antenna element, we form small arrays first, then large arrays. Besides single antenna element, feed network design also requires a number of challenges to meet low-loss, wideband and phasing requirements. The most straightforward design of feed network is the use of low-loss microstrip lines with power dividers/combiners. However, at Ku band these microstrip lines become too lossy so that array antenna becomes almost useless. A combination of microstrip feed network and waveguide feed network, therefore, is ideal. Then, the main question is how one can form the subarrays and their accompanying waveguide feed network. This thesis answers that question by formulating the subarray and array feed network loss as an optimization problem with constraints on the size and the weight of the array. With all these improvements in the antenna element and the feed network design, the array antenna exhibits 16.5% bandwidth and has 28.4 - 31.3 dBi gain for both vertical and horizontal polarizations. Overall height of the planar antenna with waveguide feed network is under 25 mm. The antenna is built and tested for reception quality. The carrier-to-noise ratio of 9.5 dB is observed for the target transponder (42° E) at 11.9 GHz using IF loop-out of the receiver.