Patent ID: 7130357

Claim:
An error compensating apparatus for an analog quadrature modulator (AQM), comprising: an error compensating unit configured to compensate predistorted I/Q digital signals according to an error compensating signal; a digital/analog converter coupled to convert outputted I/Q digital signals from the error compensating unit into I/Q analog signals; a modulator coupled to frequency modulate the I/Q analog signals outputted from the digital/analog converter; a power amplifier coupled to amplify an output signal of the modulator; a down converter to down convert a frequency of a signal coupled from the power amplifier; an analog/digital converter coupled to convert an analog output signal of the down converter into a digital signal; a demodulator coupled to divide the digital signal received from the analog/digital converter into I/Q digital signals; and a digital signal processor configured to calculate an error compensating signal by processing the I/Q digital signals outputted from the demodulator, and provide the error compensating signal to the error compensating unit, wherein the digital signal processor detects a DC offset signal by averaging sampling values of the I/Q digital signals outputted from the demodulator, and wherein the error compensating unit detects a gain compensating signal using a maximum value in a period of the I/Q digital signals of which the DC offset is compensated, detects a phase compensating value of the I/Q digital signals based on a sum of absolute values for differences between the gain compensated I-digital signals and Q-digital signals, and compensates AQM error by removing a gain error and the DC offset, after compensating a phase error of the inputted digital signal.