# Digital Cancellation of Passive Intermodulation in FDD Transceivers

## TL;DR

This paper introduces a digital cancellation method for passive intermodulation distortion in FDD transceivers, enhancing receiver sensitivity in LTE-Advanced and 5G networks by modeling PIM effects and demonstrating effective suppression through real RF measurements.

## Contribution

It develops advanced baseband models for PIM distortion considering memory effects and proposes a digital cancellation technique validated with real RF data.

## Key findings

- Digital cancellation significantly reduces PIM-induced interference.
- The method improves receiver sensitivity in LTE-Advanced and 5G FDD systems.
- Experimental results show excellent suppression of PIM in real measurements.

## Abstract

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.