Bounds and Algorithm for Direction Nding of Phase Modulated Signals

In many cases where direction nding is of interest, the signals impinging on an antenna array are known to be phase modulated, hence to have a constant mod-ulus (CM). This is a strong property, by itself already suucient for source separation, and can be used to construct improved direction nding algorithms. We rst present the relevant Cramer-Rao bounds for arbitrary array conngurations, and arbitrary number of signals and then specialize to uniform linear arrays with a single source. We then propose a simple subop-timal direction estimation algorithm, in which the signals are separated using the CM property only. Compared to the ESPRIT algorithm and to the Cramer-Rao bound for arbitrary signals, the algorithm shows good results.