Analysis of spectrum variability in sea clutter

Naval radar systems commonly employ Doppler processing to separate targets from clutter. A widely used system is the moving target detector or MTD system (Skolnik 1981) which performs a frequency analysis of a sequence of returns in each range gate. A threshold is then determined by some form of constant false alarm rate (CFAR) algorithm for the contents of each Doppler channel based on the returns in neighbouring range gates. It is normally assumed that the clutter spectrum is the same in each range gate; however, if this is not the case, it will clearly affect the threshold-setting process. It has been shown previously by Miller (2000) that there may be considerable variation in spectra for sea clutter observed at low grazing angles. In the above paper, an initial attempt was made to model this variability. The current paper applies this model to data collected by QinetiQ, Portsdown West and discusses enhancements to the original model.