Least Squares Estimation for the Digital Compensation of Tx Leakage in zero-IF Receivers

Frotzscher, Andreas; Fettweis, Gerhard

doi:10.1109/glocom.2009.5426118

Cited by 11 publications

(11 citation statements)

References 9 publications

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“…t=nT Rx (19) This reference of power P u is synthesized in the reference generator (see Figure 1) from the baseband Tx samples, and it can be noted that in practice, it might need additional processing, such as an upsampler, filters, and a resampler. Based on the observation model described in (17), the TxL channel evolution described in (12) and (13), and the reference in (19), the estimation process consists of the estimation of the time-varying complex gain β TxL (n) and the fractional delay δ. The estimation error is defined by:…”

Section: Observation Model and Estimation Objectivesmentioning

confidence: 99%

“…These methods are based on the knowledge of the transmitted signal and require the estimation of the so-called TxL channel that characterizes the Tx-Rx isolation of the duplexer and the Rx path. Different channel models are used in the literature, from a single constant coefficient [5,16], to an exponential decay filter [17], or a more general finite impulse response filter [9]. However, literature methods do not take into account that the duplexer isolation is time varying, as showed by [18].…”

Section: Introductionmentioning

confidence: 99%

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Performance of a digital transmitter leakage LMS-based cancellation algorithm for multi-standard radio-frequency transceivers

Gerzaguet

Ros

Belvèze

et al. 2016

Digital Signal Processing

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International audienceThis paper deals with a joint estimation algorithm that is dedicated to digital compensation of transmitter leakage pollution in frequency division duplexing transceivers. These transceivers are affected by transmitter to receiver signal leakage. Combined with the nonlinearity of amplifying components in the receiver path, the baseband signal received can be severely polluted by a baseband polluting term. This term is based on the square modulus of the transmitted signal, and it depends on the equivalent transmitter leakage channel which models leakages and the receiver path. Here, we consider a nonconvolutive, time-varying channel that is modeled by a time-varying complex gain and the presence of a fractional delay, modeling the propagation effects into the receiver. The complex gain is a sum of two components, a constant term that models static effects, and a first-order autoregressive model that approximates the time variation of the transmitter leakage channel. We focus here on a fully digital approach, using digital signal processing techniques and knowledge of the transmitted samples to mitigate the pollution. We first express the asymptotic performance of a transmitter leakage gain estimator piloted by a reference-based least-mean-square (LMS) approach in the synchronized case, and then we derive the influence of the fractional delay. We show that, in practice, the fractional delay cannot be neglected, and we propose a joint estimation of the fractional delay and the transmitter leakage gain to perform digital compensation. The proposed method is adaptive, recursive and online, and it has low complexity. This algorithm, that is developed for a flat transmitter leakage channel case, is seen to be robust in a typical selective channel simulation case, and more suitable than a classic multi-tap LMS scheme proposed in the literature

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Section: Observation Model and Estimation Objectivesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Performance of a digital transmitter leakage LMS-based cancellation algorithm for multi-standard radio-frequency transceivers

Gerzaguet

Ros

Belvèze

et al. 2016

Digital Signal Processing

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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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“…There are many publications available on reduction of the Tx leakage using active cancellation [2]- [8]. The baseband cancellation presented in [2] has a relatively limited performance in a presence of power amplifier intermodulation products or when a Rx front-end saturates due to high leakage power.…”

Section: Introductionmentioning

confidence: 99%

“…The baseband cancellation presented in [2] has a relatively limited performance in a presence of power amplifier intermodulation products or when a Rx front-end saturates due to high leakage power. The methods presented in [3]- [7] use one or two auxiliary signal paths to cancel the leakage of a circulator type of duplexer.…”

Section: Introductionmentioning

confidence: 99%

Wideband Tx Leakage Cancellation using Adaptive Delay Filter at RF Frequencies

Han

Szczepkowski

Farrell

2014

25th IET Irish Signals &Amp; Systems Conference 2014 and 2014 China-Ireland International Conference on Information and Communi

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-Transmitter leakage is caused by limited isolation between Tx and Rx paths of an frequency-division duplexing (FDD) transceiver due to use of non-ideal duplexers. As the leakage can seriously impair the performance of the receiver, it is important to increase the isolation of the existing system. A portion of the leakage falling into the Rx band can't be removed using conventional band-pass techniques, which leads to exploration of active cancellation methods. This paper presents an active Tx leakage cancellation structure with adaptive delay filter, together with a related design methodology. Based on S-parameters characterisation of a SAW duplexer, simulation results show that for 20 MHz bandwidth more than 25 dB cancellation can be achieved, for LTE band 8 carrier. The complexity of proposed cancellation structure is proportional to the characteristics of a duplexer used in the transceiver. Using finite number of elements, the number of auxiliary paths needed depends on how complex the characteristics of the duplexer are within the band of interest.

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Least Squares Estimation for the Digital Compensation of Tx Leakage in zero-IF Receivers

Cited by 11 publications

References 9 publications

Performance of a digital transmitter leakage LMS-based cancellation algorithm for multi-standard radio-frequency transceivers

Performance of a digital transmitter leakage LMS-based cancellation algorithm for multi-standard radio-frequency transceivers

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

Wideband Tx Leakage Cancellation using Adaptive Delay Filter at RF Frequencies

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