A Robust Nonlinear RLS Type Adaptive Filter for Second-Order-Intermodulation Distortion Cancellation in FDD LTE and 5G Direct Conversion Transceivers

Andreas Gebhard; Oliver Lang; Michael Lunglmayr; Christian Motz; Ram Sunil Kanumalli; Christina Auer; Thomas Paireder; Matthias Wagner; Harald Pretl; Mario Huemer

doi:10.1109/tmtt.2019.2896513

arXiv · 1807.04051

A Robust Nonlinear RLS Type Adaptive Filter for Second-Order-Intermodulation Distortion Cancellation in FDD LTE and 5G Direct Conversion Transceivers

Andreas Gebhard·Oliver Lang·Michael Lunglmayr·Christian Motz·Ram Sunil Kanumalli·Christina Auer·Thomas Paireder·Matthias Wagner·Harald Pretl·Mario Huemer

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Abstract

Transceivers operating in frequency division duplex experience a transmitter leakage (TxL) signal into the receiver due to the limited duplexer stop-band isolation. This TxL signal in combination with the second-order nonlinearity of the receive mixer may lead to a baseband (BB) second-order intermodulation distortion (IMD2) with twice the transmit signal bandwidth. In direct conversion receivers, this nonlinear IMD2 interference may cause a severe signal-to-interference-plus-noise ratio degradation of the wanted receive signal. This contribution presents a nonlinear Wiener model recursive least-squares (RLS) type adaptive filter for the cancellation of the IMD2 interference in the digital BB. The included channel-select-, and DC-notch filter at the output of the proposed adaptive filter ensure that the provided IMD2 replica includes the receiver front-end filtering. A second, robust version of the nonlinear RLS algorithm is derived which provides numerical stability for highly correlated input signals which arise in e.g. LTE-A intra-band multi-cluster transmission scenarios. The performance of the proposed algorithms is evaluated by numerical simulations and by measurement data.

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BibTeX RIS

Andreas Gebhard, Oliver Lang, Michael Lunglmayr, Christian Motz, Ram Sunil Kanumalli, Christina Auer, Thomas Paireder, Matthias Wagner, Harald Pretl, Mario Huemer. 2018-07-11. A Robust Nonlinear RLS Type Adaptive Filter for Second-Order-Intermodulation Distortion Cancellation in FDD LTE and 5G Direct Conversion Transceivers. https://doi.org/10.1109/tmtt.2019.2896513

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