An analysis of constant modulus receivers

This paper investigates connections between (nonblind) Wiener receivers and blind receivers designed by minimizing the constant modulus (CM) cost. Applicable to both T-spaced and fractionally spaced FIR equalization, the main results include 1) a test for the existence of CM local minima near Wiener receivers; 2) an analytical description of CM receivers in the neighborhood of Wiener receivers; 3) mean square error (MSE) bounds for CM receivers. When the channel matrix is invertible, we also show that the CM receiver is approximately colinear with the Wiener receiver and provide a quantitative measure of the size of neighborhoods that contain the CM receivers and the accuracy of the MSE bounds.