Digital beam forming for radar

Development of digital methods for antenna beam forming in the receiving mode of a radar can be advantageous in providing the system with a high degree of flexibility in `beam-pattern management¿ for countering e.c.m. and providing multiple functions efficiently. The justification for incorporating digital methods and various possible arrangements are discussed first. The main body of the paper is a review of the mathematical basis for operating in the digital domain, and includes an analysis of the main causes of error so that a broad assessment of the precision of the method, compared with more conventional and better documented types, can be made. The relationship between complexity of realisation on the one hand, with signal bandwidth, number of elements and number of simultaneous beams on the other, is also discussed. In this context brief comments are made on anticipated advances in device technology. The function of controlling the beam-formation process is summarised from the point of view of allowing corrections to the weight values in real time to be made to compensate for errors in the antenna, its feeds and the multiple receiving channels, and providing an adaptive control of the beam patterns to optimise performance against jamming. The paper ends with a description of the operation of a small experimental digital beam former.