Detection-tracking performance with combined waveforms

It is commonly understood that in radar or active sonar detection systems constant-frequency (CF) pulses correspond to good Doppler but poor delay resolution capability; and that linearly swept frequency (FM) pulses have the opposite behavior. Many systems are capable of both types of operation, and hence in this paper the fusion of such pulses is examined from a system point of view (i.e., tracking performance) via hybrid conditional averaging (HYCA), a new but increasingly accepted technique for evaluating tracking performance in the presence of missed detections. It is shown that tracking errors are highly dependent on the waveform used, and in many situations tracking performance using a good heterogeneous waveform is improved by an order of magnitude when compared with a scheme using a homogeneous pulse (CF or FM) with the same energy. Between the two types of FM considered (upsweep and downsweep), it is shown that the upsweep is always superior. Also investigated is an alternating-pulse system, which, while suboptimal, appears to offer robust performance.