Receiving array design for over-the-horizon radar

GEC-Marconi is building the RF and signal processing components of two over-the-horizon (OTH) HF Radars intended for wide-area surveillance of the northern maritime approaches to Australia. The paper describes the design of the large-aperture receiving arrays that are necessary for this type of radar Each radar requires a 3 km linear away of almost 500 elements, which places very stringent demands on the signal path matching, dynamic range and linearity of the electronic components. Whilst the use of a digital receiver per element and digital signal processing eases the requirement for accurate signal path matching in the beamforming process, a calibration system is still necessary in order to compensate for variability of the analogue sections of the receivers and for inaccuracies in the distribution of receiver local oscillator signals. The calibration method is described, together with the design of the digital receivers, local oscillator signal distribution system and array signal processing for what when completed, will probably become the world's most powerful HF receiving system.