A direct conversion receiver includes a detector that provides a measure
of bias offset that is caused by component mismatches in the direct
conversion mixer, and a corrective network that reduces the bias offset
based on this measure. The direct conversion mixer demodulates a
radio-frequency (RF) input signal via mixing with a local-oscillator (LO)
signal to provide a differential baseband output signal. A differential
peak detector compares the peak signal value at each side of the mixer's
differential output, and a differential integrator averages the
difference between these peak signal values to provide the measure of
bias offset. The corrective network adds a correction offset to each of
the local oscillator local oscillator paths on each of the switching
pairs that provide the differential output, but opposite to the local
oscillator connections. By applying the correction offset to the opposing
transistor in each pair, the difference in switching time between the
pairs is reduced, and, correspondingly, the differential-mode leakage
from the local oscillator to the RF input stage is reduced.