A four-element VHF adaptive array processor

The extension of two-element adaptive interference cancellation arrays at VHF to a four-element array is described. Here, the bulk of the processing is carried out at IF and baseband, and the processor is tuned synchronously with the VHF receiver using an external local oscillator. The analog parts of the system employ conventional RF and modular signal processing components. The principal feature of interest is the digital processing of the baseband weighting signals from the correlator, and this is described in considerable detail. Twelve-bit A/D converters are used to digitize the X and Y correlator outputs; these are preceded by low-pass filters that determine the loop step response time-constant. The external main-beam steering weights are then added to these words, and the resulting sum can be held constant in a set of digital latches to 'freeze' a particular array pattern