Adaptive interference reduction system for crosstalk cancellation in a

Abstract

An adaptive interference reduction system for removing cross talk from a dual polarization system comprising a first adjustable filter for varying the phase and the weight of a first input signal, a second adjustable filter for varying the phase and the weight of a second input signal, a first adder for adding this first input signal and the weighted and phase adjusted output from the second adjustable filter, a second adder for adding the second input signal and the weighted and phase adjusted output from the first adjustable filter, a first noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the first adder, a second noise-to-signal measuring device for generating a signal proportional to the noise-to-signal ratio in the output signal from the second adder, and a dither-type control logic for dithering in-phase and quadrature square-waves in accordance with the signals generated by the first and second noise-to-signal measuring devices to control the first and second adjustable filters. This system is further characterized in that the first and second noise-to-signal measuring devices comprise a slow response control circuit for maintaining the average value of the input signal from the adder at a reference value, and means for filtering this averaged value and detecting the power fluctuations remaining in the signal and generating a signal proportional to these fluctuations. Additionally, the first and second adjustable filters may be structured to have transfer functions across a predetermined bandwidth of W.sub.0 [1+W.sub.1 .omega.+W.sub.2 .omega..sup.2 ] or W.sub.0 [1+W.sub.1 .omega.+W.sub.2 .omega..sup.2 +W.sub.3 .omega..sup.3 ], where W.sub.0 , W.sub.1, W.sub.2 and W.sub.3 are signal weights and .omega. represents the frequency variation of the input signal from its carrier.