An HF direction finding and null steering system employing a four element circular array

Describes a small and potentially transportable HF (2-30 MHz) receiving and direction finding system which is also capable of null/beam steering. The system consists of a compact 4-element circular array, processor unit and a standard HF receiver. By using a null steering ´tree structure´ within the processor unit, the system is capable of steering a null at an interfering signal and subsequently performing DF on a wanted co-channel signal. The objectives of the system have been met by utilising the properties of circular arrays consisting of wideband active elements, adaptive signal processing techniques and microprocessor control.<>