Flat antennas for satellite terminals with tapered aperture for interference control

This paper describes a low-cost flat plate antenna that is designed to control the levels of interference from adjacent systems. The interference directions and frequencies are preset and their power levels are assumed to be bounded. A tapered amplitude and/or phase distribution across the aperture is built into the power distribution (feed network) layer of the multilayer printed circuit structure to impose nulls or low sidelobe levels in the antenna radiation pattern in the directions of the interferers. To minimize the complexity of the feed network layout, the array may be divided into identical modules or sub-arrays, each with uniform aperture distribution. The tapered distribution is applied between the sub-arrays, thus creating a quantized or stair step feeding of the modules or the sub-arrays. In general, the tapered distribution is two dimensional. However, for adjacent geostationary satellite interference, only a one-dimensional taper in the plane parallel to the orbital arc is needed. The radiation pattern discrimination in the direction of the interferers, and consequently the type of taper, depend on the link budget requirements. The taper can be Taylor, Tchebychev or any other distribution that satisfy the pattern requirements.