Direction-finding performance of the multistage CM array

The constant modulus (CM) array is a blind adaptive beamformer that steers nulls in the directions of cochannel interferers without requiring a training (pilot) signal. A cascade implementation of the system, known as the multistage CM array, is designed to recover (“copy”) several narrowband cochannel signals and provide estimates of their angles of arrival. Each stage is composed of a CM array that “captures” one of the sources and an adaptive signal canceler that removes the source from the array input. This signal cancelation influences the capture and direction finding performance of the remaining stages. The authors quantify this behavior using a stochastic model of convergence and present computer simulation results for some example source scenarios