Baseband analysis of Tx leakage in WCDMA Zero-IF-receivers

Frequency division duplex transceivers employing the zero-if principle suffers from Tx leakage. In this contribution a baseband representation of the Tx leakage impact in zero-if receivers is derived and the statistical properties of the involved baseband signals are analysed. Additionally requirements on the digital compensation of Tx leakage are discussed, based on measurement results of the Tx-Rx isolation of the duplexer as well as properties of the receive branch. Thus, a framework for the digital compensation of Tx leakage at the discrete baseband is presented. Simulation results are used to validate the theoretically predicted spectral shape of the Tx leakage impact and to evaluate the influence of Tx leakage on the system performance.