Monopulse DOA estimation using adjacent matched filter samples

In modern surveillance radar systems, amplitude comparison monopulse techniques improve target angle estimation. By comparing the difference and sum of returns from two squinted sub-beams, an angle estimate can be formed. Radars using pulse compression techniques typically use a sampled version of the matched filter output for detection and estimation purposes, and the target energy is often assumed to be contained in a single sample. In practice this assumption is often not valid; target energy is usually contained in multiple adjacent samples, and the correlation between matched filter samples is ignored. Recently, the correlation between matched filter samples has been shown useful for a variety of estimation purposes such as resolving multiple targets and fine estimation of target range. In this work, we use an explicit model for multiple adjacent matched filter samples of the sum and difference channels of a monopulse radar system, and find maximum likelihood estimates of direction of arrival for a single target. With an emphasis on low signal-to-noise and off-boresight targets, performances of the maximum likelihood estimator and generalized maximum likelihood estimator are compared to conventional monopulse techniques that use the real part of the monopulse ratio.