A four element circular array direction finding and null steering system

Describes a small and transportable HF (2-30 MHz) receiving and direction finding system which is also capable of beam/null steering. The system consists of a compact 4-element circular array, processor unit and a standard analogue HF receiver. By using a modified beamformer structure within the unit, the system is capable of direction finding, null steering, and simultaneously direction finding and null steering. It does this by pointing a null at an interfering signal and then performing DF on a wanted cochannel signal. The system is also capable of steering two independent cardioid directional patterns. The capabilities of the system have been derived by utilising the properties of circular arrays consisting of wideband active elements, adaptive signal processing techniques, and microprocessor control