Hybrid clutter cancellation method and system for improved radar

Abstract

A system is disclosed for use with radar systems so as to reduce the dynamic range requirement of the analog to digital converter through analog clutter cancellation prior to digitization. Clutter return estimates are formulated via modern digital signal processing techniques, converted to analog representation, and subtracted from the received waveform. Typically, the MTI cancellation is performed on the quadrature components of the received signal. The complex residue is then processed for target detection. This quadrature processing is not illustrated in the figures. In practice, sampling the received waveform prior to baseband down conversion, at an intermediate frequency, is also feasible. Digital synchronous detection and coherent MTI processing are then implemented in the digital signal processor. Rather than employ a radar signal processor which is either all analog or all digital it is beneficial to utilize hybrid schemes which capitalize on the advantages of both. A hybrid system is disclosed in which the acoustic delay line, which fundamentally limits analog MTI canceller performance, is replaced by a digital delay line. In effect, the transmitter crystal, delay medium, and receiver crystal are replaced by the analog to digital converter, digital delay, and digital to analog converter. The hybrid clutter canceller with digital processor and analog waveform synthesizer utilizes modern signal processing techniques to estimate the clutter return which is subtracted from the incoming analog signal. The full dynamic range of the received signal is not presented to the analog to digital converter, reducing the number of bits required for target detection in clutter. In effect, application of the hybrid clutter canceller reduces the A/D converter probability of saturation for a given A/D converter.