Digital compensation of cross-modulation distortion in multimode transceivers

In a multimode transceiver, several communication standards may be active at the same time. Owing to the small size of the transceiver, the transmitter for one standard induces a large interference on the receiver for another one. When this large interference passes through the inherently non-linear receiver front-end (FE), distortion products are generated. Among these products, the cross-modulation (CM) product is the most problematic one, as it always has the same centre frequency as the desired signal. Increasing the FE linearity to lower the CM distortion leads to unacceptable power consumption for a handheld device. Considering the continuous increase of digital computation power governed by Moore's law an attractive alternative approach is to digitally compensate for the CM distortion. An existing solution to compensate for the CM distortion is tailored to single-mode transceivers and requires an auxiliary FE. By using the locally available transmitted interference in the multimode transceiver, the authors propose a CM compensation method which requires no additional analogue hardware. Hence the power consumption and complexity of the multimode transceiver can be reduced significantly. The simulation results demonstrate that the proposed method can lower distortion to a negligible amount at realistic interference levels.