Air-Induced PIM Cancellation in FDD MIMO Transceivers

In this paper, air-induced passive intermodulation (PIM) modeling and cancellation schemes are presented in multiple-input multiple-output (MIMO) frequency-division duplexing (FDD) transceiver context. PIM is distortion generated by nonlinear passive devices either within the transmitter (TX) chain, or outside the transceiver system, as is the case in air-induced PIM. In FDD systems, the PIM products may lie on the receiver (RX) band, thus possibly desensitizing the RX chain. Unlike previous PIM cancellation works, we consider a challenging rank-2 dual-carrier MIMO transceiver scenario, with two spatially multiplexed signals per component carrier. Stemming from the PIM modeling, we first present a cancellation method based on complete set of identified basis functions (BFs). Additionally, to relax the processing complexity, we propose an alternative canceller solution with reduced number of BFs, inspired by the problem modeling. RF measurements conducted with real-life equipment indicate favorable PIM suppression levels of 20 dB using both introduced techniques.