Adaptive calibration of IIP2 in direct down-conversion mixers with modified LMS algorithm

A new adaptive calibration scheme for IIP2 in direct down-conversion mixers is proposed for reduced implementation complexity and improved convergence time. The proposed IIP2 adaptive calibration scheme utilizes a modified least-mean-squares (LMS) algorithm with a variable update step and a highly IMD2-correlated reference input. Detailed implementation of the proposed IIP2 adaptive calibration is presented. Simulation results show that the proposed IIP2 adaptive calibration achieves a 40 dB suppression of mixer´s IMD2 and a 50 μ_s convergence time, which is 100 times faster than that of a conventional LMS adaptive algorithm.