Simplified complex LMS algorithm for the cancellation of second-order TX intermodulation distortions in homodyne receivers

Lederer, Christian; Huemer, Mario

doi:10.1109/acssc.2011.6190058

Cited by 15 publications

(9 citation statements)

References 6 publications

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“…This is in contrast to the existing schemes [24,25], where the original Tx signal is used to estimate the IMD2 interference. As will be shown below, the proposed Tx-IMD2 cancellation scheme has a very low complexity employing only a single tap filter to estimate the interference.…”

Section: Stage 2: Tx-imd2 Cancellationmentioning

confidence: 94%

“…Another critical issue that appears is the Tx modulated spur interference problem that occurs in LTE-CA frequency division duplex (FDD) transceivers [22,23]. In addition, due to the non-linearities in the receiver Tx-induced second order intermodulation distortion (IMD2) interference can appear [24,25]. In the remaining part of this article, we focus on a novel joint mitigation of Tx-modulated spur and IMD2 interference for LTE-CA direct-conversion receivers.…”

Section: Fig 2 Tx Induced Modulated Spurs and Imd2 Interference Illmentioning

confidence: 99%

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Digitally-intensive transceivers for future mobile communications—emerging trends and challenges

Kanumalli

Buckel

Preissl

et al. 2018

Elektrotech. Inftech.

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This article presents an overview of the major trends and challenges involved with the design of multi-band, multi-standard digitallyintensive radio frequency transceivers for next generation mobile communications. In addition, we discuss in detail one aspect of the implementation challenges, namely the occurrence and cancellation of self-interference especially in carrier aggregation modes. For that, we present a novel digital cancellation technique to jointly compensate the self-interference caused by transmit (Tx) modulated spurs and Tx second order intermodulation distortion products (IMD2) in the receiver. This architecture exploits the underlying relation between both types of interference and offers a low-complexity solution to mitigate the Tx-IMD2 interference. Simulation results show, that the proposed technique significantly suppresses both types of interference and restores the signal-to-noise ratio of the wanted signal within 0.3 dB from its value in the absence of interference, thereby achieving 30 dB of cancellation.Keywords: RF; mobile communications; wireless communications; signal processing; interference cancellation; carrier aggregation Digital unterstützte Hochfrequenz-Transceiver für den Mobilfunk der Zukunft -Trends und Herausforderungen. Dieser Artikel gibt zunächst einen Überblick über aktuellen Trends und Herausforderungen bei der Entwicklung von Multi-Band, Multi-Standard HF-Transceivern für die nächste Mobilfunk-Generation, die einen hohen Anteil an digitaler Elektronik aufweisen. Im Anschluss wird im Detail auf ein spezielles Problem solcher Transceiver eingegangen, nämlich der Selbst-Interferenz, die durch den eigenen Sender verursacht wird und die vor allem im Carrier Aggregation-Modus auftritt. Die Problematik wird nicht nur detailliert erklärt, diese Arbeit präsentiert auch eine Methode zur Unterdrückung von Selbst-Interferenz mit den Mitteln der digitalen

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Section: Stage 2: Tx-imd2 Cancellationmentioning

confidence: 94%

Section: Fig 2 Tx Induced Modulated Spurs and Imd2 Interference Illmentioning

confidence: 99%

Digitally-intensive transceivers for future mobile communications—emerging trends and challenges

Kanumalli

Buckel

Preissl

et al. 2018

Elektrotech. Inftech.

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“…Equivalent to the channel, the OCT is fed by the chirp signal and downconverted with the instantaneous transmit signal. The resulting lowpass filtered IF signal is then given as (8) with…”

Section: E Artificial On-chip Target For Short-range Leakage Cancelamentioning

confidence: 99%

“…For instance, in [6] a leakage canceler for an RFID reader implemented on a single chip is proposed. Differently, [7], [8] proposes a concept to cancel second-order intermodulation products originating from the portion of the transmit signal leaking into the receive path in UMTS and LTE transceivers. The proposed methods partly employ similar concepts for leakage cancelation as compared to such that cancel the DC offset issue in FMCW radar systems [2], [3].…”

Section: Introductionmentioning

confidence: 99%

Short-Range Leakage Cancelation in FMCW Radar Transceivers Using an Artificial On-Chip Target

Melzer

Onic²,

Starzer³

et al. 2015

IEEE J. Sel. Top. Signal Process.

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A major drawback of frequency modulated continuous-wave (FMCW) radar systems is the permanent leakage from the transmit into the receive path. Besides leakage within the radar device itself, signal reflections from a fixed object in front of the antennas additionally introduce so-called short-range (SR) leakage. It causes a strong degradation of detection sensitivity due to the unpreventable phase noise of the transmit oscillator. In this work, we introduce an artificial on-chip target (OCT) to mitigate the SR leakage. The OCT consists of a delay line whose time delay is significantly smaller than the round-trip delay time of the SR leakage. This is motivated by the fact that in integrated circuits for automotive radar applications operating at 77 GHz delay lines in the range of only a few picoseconds can be realized with a reasonable amount of circuitry. Despite this constraint, we show that the proposed method achieves almost perfect cancelation of the SR leakage. The concept is based on the cross-correlation properties of the residual phase noise in the intermediate frequency (IF) domain. Further, the effectiveness of the proposed method is verified in an FMCW radar system simulation. It almost perfectly shows that a gain in sensitivity of approximately 6 dB is achieved, compensating for the performance degradation caused by the SR leakage. The novel leakage cancelation concept is carried out mainly in the digital domain enabling high flexibility and adaptivity.Index Terms-Digital signal processing, frequency modulated continuous-wave (FMCW) radar, leakage cancelation, phase noise, reflected power canceler.

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“…Consequently, the IMD2 interference related DC is removed from the received signal which complicates the IMD2 replica estimation. This DC removal is considered in [6,11], and neglected in [7]- [9,14]. [6] with improved steady-state cancellation and convergence speed.…”

Section: Introductionmentioning

confidence: 99%

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

Gebhard

Lang

Lunglmayr

et al. 2019

IEEE Trans. Microwave Theory Techn.

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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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Simplified complex LMS algorithm for the cancellation of second-order TX intermodulation distortions in homodyne receivers

Cited by 15 publications

References 6 publications

Digitally-intensive transceivers for future mobile communications—emerging trends and challenges

Digitally-intensive transceivers for future mobile communications—emerging trends and challenges

Short-Range Leakage Cancelation in FMCW Radar Transceivers Using an Artificial On-Chip Target

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

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