Simplified complex LMS algorithm for the cancellation of second-order TX intermodulation distortions in homodyne receivers

Intermodulation distortions are produced by a modulated blocker signal with a non-constant envelope travelling through non-linear analog stages. Especially in homodyne receivers (RX) the second-order intermodulation distortions (IMD2) are problematic since they overlay the wanted RX baseband signal. In this paper an approach to cancel the transmitter (TX) induced IMD2 in the digital domain is presented. Furthermore, it is shown that the cancellation of IMD2 can be performed independently for the in-phase (I) and quadrature (Q) component of the complex RX baseband signal. The performance of the proposed cancellation approach is verified on measured RX data of a UMTS transceiver chip.