TABLE OF CONTENTS A radar is often required to detect targets against a changing background of clutter and thermal noise, the clutter reflectivity and statistics varying with range and look direction, dependent on the chosen radar parameters, operating height and the prevailing weather conditions. For a scanning radar over the sea, this change is continuous and usually unpredictable.
The problem faced by the radar signal processing is that of reliably detecting targets, while at the same time rejecting the returns from the sea and thermal noise. To do this, we must monitor features in the radar returns that allow us to discriminate between real and spurious target returns. The final discrimination is usually done on the basis of amplitude at a detection threshold. The choice of the quantity that is thresholded depends on the signal processing and the features chosen to discriminate between real and false targets. A wide range of such features may be exploited in this way, and are associated with different types of signal processing.
Typical signal processing schemes include:
pulse-to-pulse integration
scan-to-scan integration
polarisation discrimination
Doppler processing
Pulse-to-pulse integration exploits differences in amplitude statistics and pulse-to-pulse correlation between targets and clutter or noise. Against thermal noise the gain can be quantified in term of an effective increase of power on the target.
Scan-to-scan integration is often used to exploit the longer term correlation characteristics of targets and clutter. In particular, discrete clutter spikes may not be affected by pulse-to-pulse integration, and appear to be target-like. However, such...
