System and method to calibrate the frequency response of an electronic filter

Abstract

A system and method provide for calibrating the frequency response of an electronic filter. The system and method include a radio transmitter with both in-phase and quadrature baseband paths. Each baseband path includes a numerically controlled oscillator ('NCO'), a digital signal path, a digital-to-analog converter ('DAC'), and an analog filter. A low frequency tone is applied from the NCO from one of the baseband path, while a high frequency tone is applied from the NCO in the other baseband path. An analog peak detector at output determines which analog filter has the largest amplitude at the output. The peak detector offset between the two analog filters is offset by stimulating the in-phase and quadrature baseband paths with the respective NCOs to find an amplitude difference between the output signals from the NCOs that makes the output of the analog filters the same. Calibration is then performed on the corner frequency and filter peaking through respective stimulation of the in-phase and quadrature baseband paths. The system and method is advantageous as it allows for very accurate calibration of both the filter corner frequency and peaking during a standard transmission operating mode with little additional hardware required.