The use of polarisation to enhance target to clutter ratios

An important requirement for a number of millimetre-wave radar applications is an ability to separate man-made targets from natural terrain. There is also often a requirement to minimise the cost of such sensors. One way of minimising the cost is to implement the sensor using only a single transmitter and receiver polarisation. The key question within the design of such a sensor is the choice of the polarisations for the transmitter and receiver. These should be chosen to maximise the contrast between the required target and the background. We consider the identification of the optimal polarisation configurations for detecting civilian vehicles against a background of trees. The target to clutter (T/C) ratio achieved using the optimal configuration is then compared to the maximum achieved using two constrained radar configurations; co-polar and cross-polar transmitter and receiver polarisations. This allows an evaluation of the T/C reduction incurred through the use of common and easily implemented single polarisation radars. Three types of vehicle are considered; a van, a small family car and a Landrover. For each class of vehicle results are presented illustrating the variation in the average T/C ratio with the polarimetric configuration of the radar