LMS based digital cancellation of second-order TX intermodulation products in homodyne receivers

Second-order intermodulation products are produced by non-linearities in the transfer functions of the receiver´s signal processing blocks. Especially in homodyne receivers the second-order intermodulations are problematic since they are convolved into baseband and overlap the wanted signal. In this paper a Least-Mean-Square (LMS) adaptive filter approach to estimate and cancel the transmitter (TX) induced second-order intermodulation distortion (IMD2) in the digital domain is presented. The performance of the proposed cancellation method and its dependency on the number of used filter coefficients is verified on measured data of the digital front end (DFE) output of an UMTS transceiver chip.