  Modern radio systems and transceivers utilize carrier aggregation (CA) to
meet the demands for higher and higher data rates. However, the adoption of CA
in the existing Long Term Evolution (LTE)-Advanced and emerging 5G New Radio
(NR) mobile networks, in case of frequency division duplexing (FDD), may incur
self-interference challenges with certain band combinations. More specifically,
the nonlinear distortion products of the transmit signals or component carriers
(CCs), stemming from the passive radio frequency (RF) front-end components of
the transceiver, can appear in one or more of the configured receiver bands,
potentially leading to the receiver desensitization. In this paper, we present
advanced baseband equivalent signal models for such passive intermodulation
(PIM) distortion viewed from the RX point of view, considering also potential
memory effects in the PIM generation. Then, building on these signal models, a
digital self-interference cancellation technique operating in the transceiver
digital front-end is presented. The performance of the proposed solution is
evaluated with real-life RF measurements for LTE-Advanced type user equipment
(UE) with dual CC inter-band CA, demonstrating excellent suppression
properties. The findings in this work indicate that digital cancellation is a
feasible approach for improving the receiver sensitivity of mobile devices that
may be prone to RF front-end induced PIM challenges.
