Patent ID: 7746186

Claim:
A wideband quadrature imbalance error compensation system, comprising: an in-phase channel for receiving an in-phase input, the in-phase channel having a first in-phase filter circuit; a quadrature channel for receiving a quadrature input, the quadrature channel having a first quadrature filter circuit; a first cross-coupled filter responsive to the quadrature input; a second cross-coupled filter responsive to the in-phase input; a first in-phase summing circuit responsive to the first in-phase filter circuit and the first cross-coupled filter to provide a first complex signal; a first quadrature summing circuit responsive to the first quadrature filter circuit and the second cross-coupled filter to provide a second complex signal; a complex circuit for rotating the second complex signal by 90°; a first output summing circuit responsive to the first complex signal and second rotated complex signal to provide a quadrature output pre-compensated for a quadrature imbalance error in an output of a quadrature modulator; and a phase quadrature estimator for determining the coefficients of the first and second cross-coupled filters to minimize the quadrature imbalance error; wherein the phase quadrature estimator includes: a comparator responsive to the output of the quadrature modulator and an estimate of the output of the quadrature modulator to determine a residual quadrature imbalance error; and a least mean square estimator responsive to the residual quadrature imbalance error and an input of the wideband quadrature imbalance error compensation system to update the coefficients of the first and second cross-coupled filters.