Patent ID: 6330290
Filing Date: 2001-12-11
Classification: H03D,H04B,H04L

Abstract:
In a communications terminal having an image reject mixing arrangement a compensation system for providing compensation for phase and amplitude imbalances caused by a demodulating local oscillator employed in the communications terminal, said compensation system comprising:a radio-frequency (RF) mixing stage including an in-phase and a quadrature phase branch, configured to receive a radio frequency signal and down convert said radio frequency signal to in-phase and quadrature phase intermediate frequency (IF) signals;a phase splitter unit coupled to said radio-frequency (RF) mixing stage and configured to provide an in-phase local oscillator signal and a quadrature phase local oscillator signal to said RF mixing stage, said phase splitter causing an amplitude imbalance signal .DELTA. and a phase imbalance signal .phi. to be generated in said in-phase and quadrature phase branch of said RF mixing stage;a processing circuit coupled to said RF mixing stage and configured to measure a first value associated with said amplitude imbalance and a second value associated with said phase imbalance;a phase splitter compensation unit coupled to said RF mixing stage and configured to multiply said in-phase and quadrature phase signals provided by said RF mixing stage by a predetermined compensation factor associated with said measured first and second values; andan intermediate frequency (IF) mixing stage coupled to said radio-frequency mixing stage via said phase splitter compensation unit, said IF mixing stage configured to convert said intermediate signals received from said RF mixing stage to base band frequency region.