System for compensating cross-polarized waves to attenuate crosstalk

Abstract

Polarization distortion experienced by cross-polarized waves is corrected to reduce crosstalk by transmission of pilot signals representing each of the cross-polarized waves, reception of the pilot signals and, based upon their vector values, adjustment of variable phase shifter circuits and variable attenuator circuits to minimize crosstalk effect. Received cross-polarized waves initially undergo phase compensation and are thereafter separated, amplified and then undergo a selected amount of attenuation, based on the received pilot signals, whereupon the attenuated signal of one polarized wave is mixed with the other polarized wave to eliminate the crosstalk components from each of the polarized waves. An additional phase shift adjustment may also be provided for after the cross-polarized waves undergo preamplification. The phase shifting circuits are also adjusted by the control circuits in accordance with the values of the received pilot signals. Preadjustment of cross-polarized waves may be undertaken prior to transmission thereof so that the overall effect of the adjustment of phase and amplitude prior to transmission and the polarization distortion occurring as a result of transmission offset one another to thereby deliver cross-polarized signals to a receiver in which cross-talk is substantially attenuated without further treatment of the cross-polarized waves at the receiver end. The level of phase and amplitude preadjustment at the transmitter is determined by the receipt of pilot signals from the transmitter of the remote transmitter-receiver in communication therewith.