Use of Mills cross receiving arrays in radar systems

The use of Mills cross arrays has been found to be an important contribution to radio astronomy, where accurate angular resolution in azimuth and elevation can be achieved without prohibitive costs. An analysis is made of methods for applying a Mills cross array to radar. Such an array could consist of two linear arrays positioned at right angles to each other. The arrays have fan-shaped directivity patterns, which are swept across a given sector at different rates. The result is to provide the intersection of the two beams with a raster sweep. A receiving array has been constructed to demonstrate the essential difficulties of processing radar-echo signals. Mathematical analysis gives the output of an array correlator in the form of probability density functions, assuming certain characteristis of the target signals. The calculations are extended to the performance of pulse-to-pulse integrators. On a basis of detection probability and false-alarm rate, a correlator cross array is compared with an additive array, and it is shown that, in the case of a single target, the correlation technique may be preferable. It is concluded that there can be a limited application of such techniques, depending on target density and the nature of interfering signals.