A matrix clutter processor for agile beam radars

Abstract

The removal of ground clutter from a Doppler shifted radar echo is examined from a non-traditional point of view that is particularly apt for an agile beam radar and digital signal processing. The observation in such a radar is, for each range sample, a finite duration sequence of complex envelope values. Thus, the observation is a complex vector. Clutter removal is the act of operating upon the observation vector to produce another vector that has its clutter component eliminated or substantially reduced. The operation is a matrix transformation that is, essentially, the inverse of the covariance matrix of the interference-noise plus clutter. The resulting vector is then applied to a bank of Doppler processes to produce: (a) test statistics for target detection; (b) spectral analysis to get the spectral moments of meteorological echo. The matrix processing approach removes the necessity for such things as initialization of the clutter filter. Spectral analysis is emphasized. The frequency response, clutter attenuation, and clutter improvement factor are defined in view of the matrix processing approach. In addition, the bias to be expected because of the clutter and its removal are analyzed and graphs are presented showing the bias to be expected for various spectral widths of clutter versus the frequency "notch" width of the matrix processor.