Joint-Bin Monopulse Processing of Rayleigh Targets

Amplitude comparison monopulse systems provide precision angle localization of a target. In practice, the in-phase part of the monopulse ratio is commonly used for direction-of-arrival (DOA) estimation due to simplicity and computational speed, but it suffers poor performance for off-boresight and/or low signal-to-noise ratio (SNR) targets. Target energy is typically assumed to be contained in a single range bin, while in practice the matched filter sampling process often results in multiple adjacent matched filter samples with target energy. In the traditional radar literature, this is called bin straddling and is typically treated as a nuisance—an undesired loss of signal energy. Recent literature has addressed bin straddling for DOA and range estimation for the case of multiple unresolved targets. However, error variance reports on those target estimates, which are required by target tracking algorithms, are not provided. Furthermore, target strength is assumed to be a known parameter, which is often not valid in practice. Here, we explicitly incorporate sampling into the statistical model for sum and difference channel signal samples, and derive estimators for the unknown range and unknown DOA of a single Rayleigh target. Closed-form Cramer-Rao lower bounds (CRLBs) on those estimators are provided. Furthermore, we propose the generalized CRLB (GCRLB) as an error variance report, and SNRs required for statistical efficiency and variance consistency are provided.