Frequency Estimation in Coherent, Periodic Pulse Trains

Radars use coherence to increase the signal-processing gain. In electronic support, that same coherence can be exploited to accurately estimate carrier frequency when measured modulo the pulse repetition frequency. Such estimates can be used for passive emitter geolocation, for example. In the pioneering work of Howard & Lavoie on this topic [1], [2], results are demonstrated only where the pulse repetition interval (PRI) is an integer and where pulses are sinusoidal. In this paper, we show how the results can be generalised to a broad class of pulse shapes, without needing to know the pulse shape in advance. We also show how the signals may be efficiently processed when the PRI is non-integer.