Patent ID: 8676145
Filing Date: 2014-03-18
Classification: H03D,H04B

Abstract:
1. A method in a receiver for correcting a differential output mismatch in a CMOS balanced mixer circuit, comprising: determining a strength of an interferer signal received by the receiver relative to a predetermined threshold, and, if the strength is above the predetermined threshold: a) applying a fixed voltage at a gate of at least one device of the mixer circuit, the mixer circuit comprising a pair of differential signal inputs that input a pair of RF differential signals and a pair of differential signal outputs that output a pair of zero-IF differential signals converted by the mixer circuit from the pair of RF differential signals; b) applying a compensating voltage at a gate of at least another device of the mixer circuit; c) determining any difference between differential signal voltages outputted by the pair of differential signal outputs of the mixer circuit; d) based on said difference, using a digital signal processor (DSP) to perform measurement of a value of an input-related second order intercept point of the mixer circuit; e) using the DSP to output a digital signal in response to said measurement, the digital signal selected from a plurality of digital signals stored in the DSP; f) based on the digital signal outputted by the DSP, changing a value of the compensating voltage at the gate of the at least another device; g) repeating steps b) to f) for a preselected plurality number of times; h) using the DSP to determine which one value of the compensating voltage applied at the gate of the at least another device produces a minimum second order intermodulation distortion in the receiver; and i) operating the mixer circuit while the voltage at the gate of the at least another device is at the one value of the compensating voltage that produces the minimum second order intermodulation distortion in the receiver; and if the strength is below the predetermined threshold: operating the mixer circuit without attempting to provide input-related second order intercept point correction of the mixer circuit.