Digital correction of frequency response mismatches in 2-channel time-interleaved ADCs using adaptive I/Q signal processing (original) (raw)
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Die Leistungsfähigkeit moderner Kommunikationssysteme hängt stark von den eingesetzten Analog-Digital-Umsetzer (ADU) ab, und um die Flexibilität und Genauigkeit neuartiger Kommunikationstechnologien zu ermöglichen, sind Hochleistungs-Analog-Digital-Wandler erforderlich. In dieser Hinsicht, können zeitlich versetzt operierende ADUs (ZV-ADU) eine angemessene Lösung darstellen. Bei einem ZV-ADU erhöht sich der Datendurchsatz, indem M ADU Kanäle oder Subwandler parallel eingesetzt werden und das Eingangssignal zeitlich versetzt gewandelt wird. Die Leistungsfähigkeit des ZV-ADUs wird durch ungleiche ADU Kanäle stark herabgesetzt. Diese Fehlanpassung der ADU Kanäle verfälscht das Ausgangsspektrum des ZV-ADU, indem unerwünschte Komponenten zusätzlich zu den eigentlichen Signalkomponenten generiert werden. Diese Arbeit befasst sich mit einer im Hintergrund ablaufenden adaptiven Kalibrierung von fehlangepassten Frequenzantworten eines ZV-ADUs. Indem jeder ADU Kanal als lineares zeitinvariantes System modelliert wird, entwickeln wir zeitkontinuierliche, zeitdiskrete und zeitvariante Modelle eines ZV-ADUs. Unter Zuhilfenahme dieser Modelle wird das Verhalten des ZV-ADUs mit fehlangepassten Frequenzantworten charakterisiert. Zu Beginn wird die Fehlanpassung der Frequenzantworten ausschließlich durch Verstärkungsund Abtastfehlanpassungen modelliert, welche durch Taylor Reihen erster Ordnung angenähert werden. Wir entwerfen anschließend eine blinde im Hintergrund operierende Kalibrierungsstruktur, die einen filtered-X least-mean square (FxLMS) Algorithmus einsetzt um die Verstärkungs-und Abtastfehlanpassungen zu kalibrieren. Neben ihrer Einfachheit und guten Skalierbarkeit funktioniert diese Kalibrierungstechnik auch gut für verschiedene Arten von Eingangssignalen und verbessert die Leistungsfähigkeit des ZV-ADUs beträchtlich. Weiterhin wird eine im Hintergrund operierende digitale und adaptive Technik präsentiert, welche die fehlangepassten Frequenzantworten eines zwei Kanal ZV-ADUs kalibriert. Im Gegensatz zu anderen Kabibrierungstechniken, hängt unsere Kalibrierungstechnik nicht von der Art des Eingangssignals und der Modelle der Kanalfehlanpassung ab. Wir repräsentieren die Fehlanpassung der Frequenzantwort durch eine Reihe von Polynomen von konstanter Ordnung was es uns ermöglicht die Fehlanpassung der Frequenzanworten durch die Koeffizienten der Reihe zu charakterisieren.
IEEE Transactions on Circuits and Systems I-regular Papers, 2009
In this paper we present a flexible and scalable structure to compensate frequency response mismatches in timeinterleaved analog-to-digital converters (TI-ADCs). The flexibility of the structure allows for designing compensation filters independent from the number of channels that can achieve any desired SNR due to the scalability of the structure. Therefore, the compensation structure may be used to compensate timevarying frequency response mismatches in TI-ADCs as well as to reconstruct uniform samples from nonuniformly sampled signals. We analyze the compensation structure, investigate its performance, and demonstrate application areas of the structure through numerous examples.
An Adaptive Mismatch Error Cancellation Architecture for Time-Interleaved A/D Converters
2013
The Time-Interleaved Analog-to-Digital Converter (TI-ADC) is an efficient approach to systems requiring very high sampling rate with medium to high resolution. However, interchannel mismatches and process variations appear as a main bottleneck leading to substantial degradation in global TI-ADC performance. In this paper, an adaptive compensation technique is proposed for improving the overall performance in the presence of offset mismatch independent from either non-ideality origins or input signal. Proposed method is based on an adaptive Filter that verified through simulating a two-channel TI-ADC architecture. LeastMean-Squares (LMS) algorithm has been exploited as adaptation mechanism so that offset error of each channel is estimated with regard to a preselected reference channel. Proposed method is realized by a minimum hardware complexity. Besides, proposed adaptive TI-ADC is able to track slow drifts in mismatches originated from temperature variations or aging process.
An Adaptive Mismatch Error Cancellation Architecture for Time-Interleaved A/D Converters 1
2014
The Time-Interleaved Analog-to-Digital Converter (TI-ADC) is an efficient approach to systems requiring very high sampling rate with medium to high resolution. However, interchannel mismatches and process variations appear as a main bottleneck leading to substantial degradation in global TI-ADC performance. In this paper, an adaptive compensation technique is proposed for improving the overall performance in the presence of offset mismatch independent from either non-ideality origins or input signal. Proposed method is based on an adaptive Filter that verified through simulating a two-channel TI-ADC architecture. Least-Mean-Squares (LMS) algorithm has been exploited as adaptation mechanism so that offset error of each channel is estimated with regard to a preselected reference channel. Proposed method is realized by a minimum hardware complexity. Besides, proposed adaptive TI-ADC is able to track slow drifts in mismatches originated from temperature variations or aging process.
2006
Analog-to-digital converters (ADCs) are critical components of signal processing systems and one of the bottlenecks of modern telecommunication systems. Time-interleaved ADCs (TI-ADCs), in which multiple ADCs are combined, are an effective way to achieve high sampling rates in order to comply with modern telecommunication standards. The drawback of such TI-ADCs are additional errors that are due to mismatches among the channels, which degrade the overall performance. Several qualified methods have been proposed to compensate offset, static gain, and timing (or linear-phase) mismatches. However, an effective method to compensate frequency-dependent magnitude response mismatches is still missing. In this paper we consider the compensation of frequency-dependent magnitude response mismatches for a two-channel time-interleaved sampling system. A single linear-phase finite impulse response (FIR) filter cascaded by a single time-varying multiplier provides the magnitude response compensation so that the performance of a TI-ADC is no longer limited by linear channel mismatches.
Analysis and compensation of nonlinearity mismatches in time-interleaved ADC arrays
2004
Time-interleaved ADCs (TIADCs) are used to achieve high sampling rates. The drawback of such an architecture are mismatch effects, which decrease the signal-to-noise and distortion ratio (SINAD) and the spurious-free dynamic range (SFDR). Many papers have investigated the problem of mismatches but very few have considered he problem of nonlinearity mismatches. We present a mathematical framework for nonlinearity mismatches, describe their main characteristics, and show an effective compensation method to increase the SFDR.
A Review: Compensation of Mismatches in Time Interleaved Analog to Digital Converters
The execution of today's correspondence frameworks is exceedingly subject to the utilized Analog-to-Digital converters (ADCs), and with a specific end goal to give more flexibility and exactness to the developing correspondence innovations, superior-ADCs are needed. In this respect, the time-interleaved operation of an exhibit of ADCs (TI-ADC) might be a sensible result. A TI-ADC can build its throughput by utilizing M channel ADCs or sub converters in parallel and examining the data motion in a period-interleaved way. In any case, the execution of a TI-ADC gravely suffers from the bungles around the channel ADCs. In this paper we survey the advancement in the configuration of low-intricacy advanced remedy structures and calculations for time-interleaved ADCs in the course of the most recent five years. We devise a discrete-time model, state the outline issue, and finally infer the calculations and structures. Specifically, we examine proficient calculations to outline time-differing remedy filters and additionally iterative structures using polynomial based filters. Thusly, the remuneration structure may be utilized to repay time-differing recurrence reaction befuddles in timeinterleaved ADCs, and in addition to remake uniform examples from nonuniformly tested indicators. We examine the recompense structure, research its execution, and exhibit requisition zones of the structure through various illustrations. At long last, we give a standpoint to future examination questions.
On the Compensation of Magnitude Response Mismatches in M-channel Time-interleaved ADCs
2007
Parallel time-interleaved analog-to-digital converters (TI-ADCs) are an attractive architecture to realize low-power and high-speed data conversion. As a drawback of such converters, mismatches between the channels impair their performance, e.g., the spurious free dynamic range (SFDR). One characteristic that varies among all channels is the magnitude response. We have recently proposed a method to compensate magnitude response mismatches in two-channel TI-ADCs. In this paper we extend this method to an arbitrary number of channels, discuss a possible implementation, and evaluate its performance. For an M -channel TI-ADC the compensation method requires (M − 1) linear-phase FIR filters with relatively short tap sizes and (M − 1) multipliers to modulate the filter output. Simulations confirm the effectiveness of the proposed method.