Patent ID: 7280612

Claim:
A digital branch calibrator for use in an RF transmitter to compensate for phase and/or gain imbalances between two phasor fragment signals in a transmit path from a phasor fragmenter in a digital front end of said transmitter to a power amplification and combining component in an analog front end of said transmitter outputting an RF transmit signal based on a sum of said fragment signals, said calibrator comprising: (a) a closed loop controller operable during a calibration sequence, defined by a predetermined number of control loop iterations, and comprising transmit and feedback signal paths, said transmit signal path to transmit a zero base band transmit signal and said feedback signal path to receive a feedback signal correlated with a power level of said output RF transmit signal, said transmit signal path comprising a phase and/or gain adjusting component to adjust the phase and/or gain of said phasor fragment signals to minimize said power level, said adjusting being performed iteratively to the end of said calibration sequence and resulting in sequence phase and/or gain update signals, wherein said sequence update signals are provided for updating the phase and/or gain of data signals transmitted through said transmit signal path; and (b) digital signal processing means to operate said controller and to control said transmission of said zero base band transmit signal for processing by said calibrator; wherein said closed loop controller further comprises false imbalance removal means to remove from said feedback signal any portion thereof correlating to local oscillator and/or other non-imbalance feed through energy at the carrier frequency, said false imbalance removal means comprising a digital modulator/demodulator to modulate said zero base band signal by a sub-carrier frequency signal and to demodulate said feedback signal; and wherein said phase and/or gain adjusting component comprises a complex accumulator to decimate said feedback signal.