Title :
Adaptive filtering using LMS for digital TX IM2 cancellation in WCDMA receiver
Author :
Kahrizi, Masoud ; Komaili, Jaleh ; Vasa, John E. ; Agahi, Darioush
Author_Institution :
Sky works Solution Inc., Irvine
Abstract :
In this paper, a digital technique for canceling second-order inter-modulation (IM2) of transmitter (TX) leakage in WCDMA direct-conversion receivers is described. Digital TX signal is used as a reference to generate a digital IM2 signal and then is passed through the auxiliary digital filter chain as in receiver chain. Adaptive least mean square (LMS) algorithm combined with a delay estimator provides a very robust technique to act as a matched filter to estimate the channel which causes leakage from TX to RX. The delay between the receive path and the reference path is estimated by peak correlation detection. This IM2 cancellation works well even though the actual IM2 components are far below the desired signal and thermal noise.
Keywords :
adaptive filters; channel estimation; code division multiple access; filtering theory; least mean squares methods; matched filters; radio receivers; LMS; WCDMA receiver; adaptive filtering; adaptive least mean square algorithm; auxiliary digital filter chain; channel estimation; delay estimator; digital TX IM2 cancellation; direct-conversion receivers; matched filter; peak correlation detection; receive path; reference path; second-order inter-modulation; thermal noise; Adaptive filters; Auxiliary transmitters; Delay estimation; Digital filters; Leak detection; Least squares approximation; Matched filters; Multiaccess communication; Robustness; Signal generators; Adaptive filters; TX leakage; WCDMA; correlators; direct-conversion; filter and second order intercept point; least mean square; matched filter; second order intermodulation distortion;
Conference_Titel :
Radio and Wireless Symposium, 2008 IEEE
Conference_Location :
Orlando, FL
Print_ISBN :
978-1-4244-1462-8
Electronic_ISBN :
978-1-4244-1463-5
DOI :
10.1109/RWS.2008.4463543
