Interference cancellation system employing a polar vector modulator

摘要

An interference cancellation system employing a polar vector modulator obtains a reference signal and a received signal. The received signal has a desired signal component and an interfering signal component. The reference and received signals as well as an auxiliary signal of known frequency and amplitude, are provided to a signal correlator circuit which compares and correlates the reference and received signals and generates an adjusted auxiliary signal which corresponds to the auxiliary signal adjusted in phase and amplitude. A phase detector detects the difference in phase between the auxiliary signal and the adjusted auxiliary signal and generates a phase control signal in response. Likewise, an amplitude detector measures the amplitude of the adjusted auxiliary signal and generates an amplitude control signal in response. The phase and amplitude control signals and the reference signal are provided to a polar vector modulator having a 360 DEG variable phase shifter and a variable attenuator coupled together in series, each of which has a low or negligible insertion loss. The reference signal is amplitude and phase adjusted by the polar vector modulator to have substantially the same amplitude and to be 180 DEG out of phase with the interfering signal component of the received signal. The amplitude and phase adjusted reference signal is then summed with the received signal so that substantially only the desired signal component of the received signal remains.