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

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

doi:10.1109/tmtt.2019.2896513

Cited by 44 publications

(25 citation statements)

References 36 publications

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“…Here we assume a sufficiently narrow bandwidth of the shifted harmonic x PA, Hθ BB (t) e j2πf∆t and the additive noise η Rx2 BB (t) such that both are unaffected by the AAF.g sp equals 1 for ζ = 1 and g sp otherwise. Usually, direct-conversion Rx chains contain a direct current (DC) cancellation stage, which is modeled by the notch filter h dc [n] [37], [38]. In combination with the channelselect filter (CSF) h csf [n], we obtain the digital BB signal…”

Section: A Interference Modelmentioning

confidence: 99%

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

Paireder

Huemer

2021

IEEE Open J. Commun. Soc.

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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.

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Section: A Interference Modelmentioning

confidence: 99%

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

Paireder

Huemer

2021

IEEE Open J. Commun. Soc.

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“…The major advantage of RI-based algorithms over the RLS-based algorithm is the unnecessity to update the inverse autocorrelation matrix [16]. Such an update of the inverse autocorrelation matrix might cuase numerical instabilities in RLS-based algorithms [22][23][24]. Fortunately, this is not the case for the RI algorithm and its variants.…”

Section: Dwt Second-order Recursive Inverse Algorithmmentioning

confidence: 99%

Discrete-wavelet-transform recursive inverse algorithm using second-order estimation of the autocorrelation matrix

2020

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The recursive least squares (RLS) algorithm was introduced as an alternative to least mean square (LMS) algorithm with enhanced performance. Computational complexity and instability in updating the autocolleltion matrix are some of the drawbacks of the RLS algorithm that were among the reasons for the introduction of the second-order recursive inverse (RI) adaptive algorithm. The 2 nd order RI adaptive algorithm suffered from low convergence rate in certain scenarios that required a relatively small initial step-size. In this paper, we propose a new second-order RI algorithm that projects the input signal to a new domain namely discrete wavelet transform (DWT) as pre step before performing the agorthim. This transformation overcomes the low convergence rate of the second-order RI algorithm by reducing the selfcorrelation of the input signal in the mentioned scenatios. Expeirments are conducted using the noise cancellation setting. The performance of the proposed algorithm is compared to those of the RI, original second-order RI and RLS algorithms in different Gaussian and impulsive noise environments. Simulations demonstrate the superiority of the proposed algorithm in terms of convergence rate compared to those algorithms.

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“…However, recent studies suggested that the second-order intermodulation (IM) distortion may be significant in wideband transceivers widely used in long-term evolution advanced (LTE-A) and fifth-generation new radio (5G NR) systems [2][3][4][5][6][7]. In direct conversion receivers, also known as homodyne or zero-IF receivers, the second-order IM dominates in degrading the performance of the receiver by causing a severe signalto-interference-plus-noise ratio degradation of the received signal [6,7] because the regenerated second-order distortion is hard to discriminate from the desired signal [8]. Further, the second-order intercept point (IP2), which is used to quantify the second-order distortion regenerated by non-linear sys-tems and devices, appears more frequently in recent amplifier datasheets [9].…”

Section: Introductionmentioning

confidence: 99%

On IP2 impact to nonlinear distortion of RF amplifiers

Yang

Yan

et al. 2021

J. eng.

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The second-order distortion, often using second-order intercept point (IP2) as an indicator, has been considered easy to be filtered in narrowband radio frequency (RF) communications because it is located far away from the passband of transmitted signals. However, with rapidly increased applications in wideband RF communications, the secondorder intermodulation (IM) might become important, partially evidenced by the increased appearances of IP2 in the amplifier datasheets in recent years. In this article, a power spectrum model of the second-order IM is derived to quantify the second-order distortion using the IP2. This model could be used to determine under what conditions, in terms of the relation between the carrier frequency and bandwidth, the second-order IM will affect the passband or the adjacent bands or other applications, using three types of frequency scenarios. These discussions are beneficial for RF engineers and spectrum planners to predict interferences from second-order IM. The experimental measurement at the end of the article validates the spectrum model. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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

Cited by 44 publications

References 36 publications

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

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

Discrete-wavelet-transform recursive inverse algorithm using second-order estimation of the autocorrelation matrix

On IP2 impact to nonlinear distortion of RF amplifiers

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