Abstract: A method and apparatus are provided for producing multiple, frequency-addressable beams (66-80) employed in a satellite communication system. The beams (66-80) are effectively scanned over an area of the earth in order to communicatively interconnect small communication terminals on the earth. Multiple beams are formed which can be scanned independently of each other in the direction of scanning. Two or more beam formers (104, 106) are coupled in parallel and feed a single array of antenna elements. The outputs of the beam formers (104, 106) are combined in summers (98) and are then amplified by power amplifiers 38 and applied to excite the array elements (30). Phase shifters (92-96) are coupled between the beam formers (104, 106) and the array elements (30) to shift the phase of the beam signals and thereby aim or shift the beams in a direction orthogonal to the scanning direction in order to provide the desired coverage over the earth.

Abstract: A communications receiver for a code division multiple access (CDMA) satellite communication system in which a plurality of data carriers share the same band. A pilot carrier transmits a timing reference used by all receivers to acquire the clock used in timing the code generators, and used as a frequency and phase reference for data detection. This receiver employs a digital signal processor that detects a spread pilot carrier and uses the phase noise on the pilot carrier to subtract the communication link phase noise from the data carriers, thus allowing communication at lower signal-to-noise ratios.

Abstract: A steerable beam antenna system for use in satellite communication systems and including a main reflector and an antenna array having a plurality of feed elements is disclosed. The antenna array is positionable at or near at least one focal point of the main reflector, and its feed elements can receive microwaves from or transmit microwaves toward the main reflector. A Butler matrix having multiple input ports and multiple outputs is connected to the array of feed elements and substantially performs a spatial Fourier transformation on a generated set of signals to be transmitted which have a predetermined phase relationship between the signals, which is necessary to create the steerable beam. The Butler matrix also can perform an inverse spatial transformation on a set of incoming signals focused on the array by the reflector and received by the feed elements.