A note on the aperture of electrically scanned arrays

Since the size of current radar antennas must be increased in order to detect aircraft and missiles flying at supersonic speeds, it is no longer possible to use rapid mechanical scanning. Therefore this type of scanning is being gradually replaced by electrical scanning. The popular approximation which states that the effective aperture length is proportional to cos , where is the scan angle from broadside, is examined and shown to be adequate in many cases where the end-fire effect is negligible. An exact effective aperture based on half-power beamwidth is derived and compared with the approximate solution for various aperture lengths as a function of scan angle.