Patent ID: 6940916

Claim:
An apparatus that receives a digital baseband signal and modulates the digital baseband signal to a quadrature modulated output signal, the apparatus comprising: a quadrature modulator compensation signal processor (QMCSP) adapted to receive the digital baseband signal, where the QMCSP includes a first digital filter to generate a digital compensated signal so that the digital compensated signal negates at least a portion of a quadrature impairment in an analog quadrature modulator system (AQMS) for a plurality of baseband frequencies; the AQMS, where the AQMS is adapted to receive the digital compensated signal and a local oscillator signal, where the AQMS is further adapted to quadrature modulate, in analog domain, the digital compensated signal to the quadrature modulated output signal; a termination switch adapted to provide an observation signal, where the termination switch is coupled to a sample signal related to the quadrature modulated output signal and coupled to a source for a ground signal, where the termination switch further switches between the sample signal and the source for the ground signal in response to a ground switch control signal; a variable phase shifter adapted to receive the local oscillator signal and to provide a phase shifted output signal, where the phase shifted output signal is selectable to at least 3 phase shifts, and where a phase shift is selected in response to a phase shifter control signal; an analog quadrature demodulator system (AQDS) adapted to receive the observation signal and the phase shifted output signal, the AQDS adapted to demodulate the observation signal and to recover a received baseband signal that is related to the baseband signal, and where the received baseband signal includes quadrature impairment; a quadrature demodulator compensation signal processor (QDCSP) adapted to receive the received baseband signal from the AQDS, where the QDCSP includes a second digital filter to generate a demodulated baseband signal such that at least a portion of the quadrature impairment added to the received baseband signal by the AQDS is compensated in the demodulated baseband signal for a plurality of frequencies; and an adaptive control processing and compensation estimation (ACPCE) circuit adapted to monitor the baseband signal and the received baseband signal, where the ACPCE circuit is further adapted to update parameters used by the QMCSP and the QDCSP to compensate for quadrature impairment.