The design of an analogue beamformer for adaptive antennas

Abstract

An analogue beamformer for a null steering adaptive antenna has been developed for use in the receive path of an airborne communications system. The particular application poses many design challenges for the beamformer, namely broad bandwidth, wide dynamic range, high weight accuracy and resolution, and rapid weight settling time. In addition to these requirements, the beamformer needs to be of low cost with the intention of reuse in a commercial application. The beamformer has been simulated, built and has undergone extensive testing. The results obtained from the beamformer in `stand-alone' mode and within an adaptive loop, show the design challenges were all successfully met using a PIN diode based analogue beamformer design. The exceptional weight accuracy was achieved by a combination of a novel analogue linearising circuit and a digital look-up table. The dearest testament to the successful design of the beamformer is its performance within the adaptive loop, where the speed and accuracy of the beamformer achieved rapid and stable adaptation against interference. (6 pages)