Estimation of co-channel FM signals with multitarget adaptive phase-locked loops and antenna arrays

A simple adaptive technique is proposed for separation and demodulation of multiple co-channel frequency modulated (FM) signals received at an antenna array. The proposed method, which for FM signals is embodied in an architecture referred to as a multitarget adaptive phase-lock loop (MADPLL), exploits known signal structure through a complete demodulation and remodulation of the signals. The two properties of the signal that are exploited here are the known bandwidth of the information signal and the constant-modulus (CM) property of FM signals. It is shown that the proposed method can lead to significant improvements in performance over methods that exploit only the CM property