Least Squares Estimation for the Digital Compensation of Tx Leakage in zero-IF Receivers

Transmitter Leakage has a significant impact on the system performance in mobile devices using zero-IF receivers and thus requires a suitable compensation. In contrast to analog approaches, digital Tx Leakage compensation approaches can easily be reconfigured and therefore are highly attractive for future mobile devices, using software defined radios. In this contribution we present a digital Tx Leakage compensation approach which uses a Least Squares estimator. The AD conversion of the Tx Leakage interference causes an additional SNR loss w.r.t. the desired received signal and thus limits the applicability of the digital Tx Leakage compensation. We show that the presented Least Squares approach reaches almost this upper limit and mitigates the Tx Leakage by 25 dB, considering a 8-bit uniform mid-rise ADC. Thus, using this approach, the system designer can allow much stronger Tx Leakage, which significantly relaxes the requirements on the linearity and the Tx-Rx isolation of the analog front end.