CLUTTER ATTENUATION ANALYSIS

Abstract

The performance of moving target indication (MTI) systems for combat surveillance radars depends to a large extent on the clutter spectrum, which is especially important when the radar attempts to detect slowly moving ground targets. This spectrum has long been assumed to be Gaussian shaped. However, MTI system performance predicted by this assumption was not achieved in practice. This report describes the results of an investigation conducted to determine the performance to be expected from an MTI system. The approach used was to measure the clutter rejection ratios afforded by various high-pass filters. The signal was taken from the boxcar demodulator of an X-band radar observing different clutter targets under varying wind conditions. Clutter rejection ratios of 10 to 40 db were measured. These results were then used to obtain a theoretical expression for the clutter power spectrum. This expression differs from the usual Gaussian assumption. Some credence is given to the results by a direct spectral analysis performed on a clutter signal. Two methods of filtering clutter signals which will result in acceptable MTI performance are suggested in this report. The results of this investigation are significant in that they have led to establishing criteria for a better MTI system design.

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