Convergence analysis of the least squares constant modulus algorithm in interference cancellation applications

The convergence behavior of the least squares constant modulus (CM) algorit hm in an adaptive beamforming application is examined. It is assumed that t he desired signal and the interference are uncorrelated, The improvement in output signal-to-interference ratio (SIR) with each iteration of the algor ithm is predicted for several different signal environments. Deterministic results are presented for an environment containing two complex sinusoids, Probabilistic results are presented for a CM desired signal with a CM inter ferer and with a Gaussian interferer. The asymptotic improvement in output SIR as the output SIR becomes high is also derived. The results of Monte Ca rlo simulations using sinusoidal, frequency modulation, and quadrature phas e-shift keying signals are included to support the derivations.