Patent ID: 7561862

Claim:
A calibration apparatus for automatically selecting a compensation value usable to reduce a second order intermodulation (IM 2 ) product in an output signal of a mixer, the calibration apparatus comprising: a mixer to output a mixed signal; a detector to detect an IM 2 product in samples corresponding to the mixed signal; and a compensation determination circuit to do the following automatically, to apply a plurality of candidate values of a mixer-control signal to the mixer, the mixer-control signal affecting a magnitude of an IM 2 product in the mixed signal, to evaluate samples from the detector corresponding to the plurality of candidate values, respectively, and to select one among the plurality candidate values as the compensation value, wherein the detector includes, an IM 2 sampler to produce the samples corresponding to the mixed signal and to generate an indication of the magnitude of an IM 2 product in the samples, respectively, and a monotonicity change sensor to detect if there is a change in a monotonic progression of samples output by the IM 2 sampler.