Low-Complex Digital Cancellation of Transmitter Harmonics in LTE-A/5G Transceivers

Abstract

Nowadays, mobile communication radio frequency transceivers for LTE-A/5G usually operate in frequency-division duplex mode and support carrier aggregation. The resulting complexity requires compromises in the analog front-end. One consequence is a limited stop-band attenuation of the duplex filters that separate the transmit and the receive paths. The resulting transmit leakage signal combined with other non-idealities, like power amplifier (PA) harmonics, can create self-interference problems that desensitize the receivers. In this work, we propose an optimized digital self-interference cancellation scheme to mitigate the unacceptable performance degradation caused by PA induced harmonics. We derive an appropriate interference model and quantify the interference power levels for a specific PA. Based on these results, our low-complex cancellation approach solely targets the dominating components. Our algorithm relies on the auto-covariance matrix for the second and third power of LTE signals, which we derive for the first time in an analytic form. This statistical information can be combined with the transform-domain concept to noticeably improve the performance of a least-mean squares based cancellation algorithm. The capabilities of the approach are demonstrated by means of simulations and are validated on measurement data.

Air-Induced Passive Intermodulation in FDD MIMO Systems: Algorithms and Measurements

“…In addition to PIM modeling and cancellation, the works in [3], [4], [25], [26], [27], [28], [29], and [30] have considered the cancellation of the intermodulation distortion imposed by active components, primarily the TX PA systems. However, these works do not consider PIM, yet it is noted that similar behavioral modeling principles apply when the source of the intermodulation distortion is an active component.…”

Adaptive System Identification via Low-Rank Tensor Decomposition

“…To evaluate the proposed models for their performance on a complex-valued system identification example, we chose the well-known case of transmitter (Tx) induced harmonics which can occur in 4G/5G cellular transceivers in the case of downlink carrier aggregation coupled with a non-ideal Tx power amplifier (PA). For more details on the exact signal model, the reader is referred to [27]. Additionally, this model simulates saturation behavior of the PA which might occur if the Tx signal power is close to the limit of the PA's dynamic range [21].…”