Impact of RF front-end non-idealities on performances of SIMO-OFDM receiver

Today, in OFDM systems, zero-IF receivers are very appealing, because they avoid costly IF filters. However, this very popular architecture implies IQ demodulation at RF and thus introduces new drawbacks and large performance degradations. It´s therefore very important to study the impact of RF front-end non- idealities on performances of OFDM receiver. Especially, it´s necessary to investigate the influence of I/Q gain and phase imbalance, local oscillator phase noise and non-linear distortion. In this paper, 802.11g standard has been studied in terms of bit error rate (BER) and constellation of each subcarrier. Simulated and measured results have been studied in the four arms SMI (sample matrix inversion) as compared with a single antenna receiver. Two channel conditions, AWGN channel and multipath channel (taking account the fading correlation), have been modelled and studied to quantify WLAN performance degradations but also to evaluate the efficiency of a multi element antennas system at the receiver to improve significantly the performances of a wireless system. Advanced design system (ADS - Agilent Technologies) software and a radio test-bed have been used in this work.