Digitally Intensive Mixed-Signal Approach for Self-Interference Cancellation in LTE-A/5G-Transceivers

State-of-the-art radio frequency transceivers for mobile communication devices suffer from transmitter-to-receiver (Tx-Rx) leakage in frequency division duplex operation, which, in combination with further non-idealities in the analog frontend, may lead to diverse self-interference (SI) effects. Digital as well as mixed-signal architectures have been proposed for self- interference cancellation. In this work we present a digitally intensive mixed-signal approach, where a low-cost auxiliary receiver senses the leaked Tx-signal. Firstly, the sensed signal is used to adaptively estimate the leakage channel, whereas in a second step a cleaned version of the leaked Tx-signal is reconstructed digitally. This reconstructed Tx-leakage signal is then used as input for a low complex adaptive interference cancellation unit to suppress modulated spurs or intermodulation distortions. We show that this approach allows to significantly relax the analog auxiliary receiver specifications, while different to conventional all-digital solutions being able to deal with multiple different types of SI with minimal configuration overhead.