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21
TimeInterleaved Oversampling A/D Converters: Theory and Practice
 IEEE Trans. Circuits Syst. II
, 1997
"... In this paper, the design procedure and practical issues regarding the realization of timeinterleaved oversampling converters are presented. Using the concept of block digital filtering, it is shown that arbitrary 16 topologies can be converted into corresponding timeinterleaved structures. Prac ..."
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In this paper, the design procedure and practical issues regarding the realization of timeinterleaved oversampling converters are presented. Using the concept of block digital filtering, it is shown that arbitrary 16 topologies can be converted into corresponding timeinterleaved structures. Practical issues such as finite opamp gain, mismatching, and dc offsets are addressed, analyzed, and practical solutions to overcome some of these problems are discussed. To verify the theoretical results, a discretecomponent prototype of a secondorder timeinterleaved 16 analog/digital (A/D) converter has been implemented and the design details as well as experimental results are presented. Index TermsConverters, timeinterleaved, oversampling. I. INTRODUCTION O VERSAMPLING converters have become a popular technique for data conversion [1]. One reason for their popularity is their outstanding linearity which comes from the fact that they usually exploit a 1b quantizer. Even with a tr...
Recovering Signals from Lowpass Data
 IEEE Trans. Signal Process
, 2010
"... Abstract—The problem of recovering a signal from its low frequency components occurs often in practical applications due to the lowpass behavior of many physical systems. Here, we study in detail conditions under which a signal can be determined from its lowfrequency content. We focus on signals in ..."
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Abstract—The problem of recovering a signal from its low frequency components occurs often in practical applications due to the lowpass behavior of many physical systems. Here, we study in detail conditions under which a signal can be determined from its lowfrequency content. We focus on signals in shiftinvariant spaces generated by multiple generators. For these signals, we derive necessary conditions on the cutoff frequency of the lowpass filter as well as necessary and sufficient conditions on the generators such that signal recovery is possible. When the lowpass content is not sufficient to determine the signal, we propose appropriate preprocessing that can improve the reconstruction ability. In particular, we show that modulating the signal with one or more mixing functions prior to lowpass filtering, can ensure the recovery of the signal in many cases, and reduces the necessary bandwidth of the filter. Index Terms—Lowpass signals, sampling, shiftinvariant spaces. I.
Architecture alternatives for timeinterleaved and inputfeedforward deltasigma modulators
, 2008
"... This thesis provides architecture alternatives for deltasigma modulators in two areas: highspeed operation based on timeinterleaving and lowvoltage environment by exploiting the inputfeedforward concept. Parallelism based on timeinterleaving can be used to increase the speed of deltasigma mod ..."
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This thesis provides architecture alternatives for deltasigma modulators in two areas: highspeed operation based on timeinterleaving and lowvoltage environment by exploiting the inputfeedforward concept. Parallelism based on timeinterleaving can be used to increase the speed of deltasigma modulators. A novel singlepath timeinterleaved architecture is derived and analyzed. Finite opamp gain and bandwidth result in a mismatch between the noise transfer functions of the internal quantizers which degrades the performance of the new modulator. Two techniques are presented to mitigate the mismatch problem: a hybrid topology where the first stage uses multiple integrators while the rest of the modulator uses a single path of integrators and a digital calibration method. The inputfeedforward technique removes the inputsignal component from the internal nodes of deltasigma modulators. The removal of the signal component reduces the signal swing and distortion requirements for the opamps. These characteristics enable the reliable implementation of deltasigma modulators in modern CMOS technology. Two implementation
A Wideband SigmaDelta Modulator With CrossCoupled TwoPaths
"... Abstract—The performance of a sigmadelta analogtodigital converter (ADC) critically depends on one or more of the main three parameters: oversampling ratio, the order of the modulators, and the number of bits used. Increasing each one of these parameters presents a degree of challenge (i.e., th ..."
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Abstract—The performance of a sigmadelta analogtodigital converter (ADC) critically depends on one or more of the main three parameters: oversampling ratio, the order of the modulators, and the number of bits used. Increasing each one of these parameters presents a degree of challenge (i.e., the increase in the oversampling ratio is limited by the technology and the power consumption requirement). This paper presents a method to obtain high order noise shaping withpath architectures that are based on firstorder or secondorder modulators. The desired noise transfer function (NTF) is obtained by suitable crosscoupling paths. The method was applied to a twopath firstorder modulator for obtaining a secondorder noise shaping. The performances of the proposed sigmadelta ADC were verified at the behavioral and transistor level implemented in 90nm CMOS technology. Index Terms—Analogtodigital conversion, data conversion, low power, noise shaping, sigma delta. I.
Broadband digitization for cable tuners frontend
 in Microwave Conference (EuMC), 2011 41st European
, 2011
"... Abstract —The RF frontend for forthcoming broadband receivers of cable modems is investigated. The aim is the digitization of the whole RF cable input spectrum, which spreads from 50MHz to 1GHz. In this paper, several architectures are proposed and evaluated. We introduce a general cost function in ..."
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Abstract —The RF frontend for forthcoming broadband receivers of cable modems is investigated. The aim is the digitization of the whole RF cable input spectrum, which spreads from 50MHz to 1GHz. In this paper, several architectures are proposed and evaluated. We introduce a general cost function in order to compare these proposals. We verify that the complete digitization of the cable input spectrum is a challenging problem, and show that a solution based on analytic signals and downconversion is promising. I.
Design, optimization and calibration of an HFBbased ADC
 in New Circuits and Systems Conference (NEWCAS), 2011 IEEE 9th International
, 2011
"... Abstract — We describe the design of an HFBbased ADC targeted towards the digitization of a very large band for Software Defined Radio applications. We present an original procedure for the optimization of the synthesis filters, when the frontend analysis filters use standard lowcost analog filte ..."
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Abstract — We describe the design of an HFBbased ADC targeted towards the digitization of a very large band for Software Defined Radio applications. We present an original procedure for the optimization of the synthesis filters, when the frontend analysis filters use standard lowcost analog filters. We also address the calibration of the device, namely the identification of the actual analog filters, and highlight the impact of the identification and of measurement errors on the overall performances. I.
> REPLACE THIS LINE WITH YOUR PAPER IDENTIFICATION NUMBER (DOUBLECLICK HERE TO EDIT) < 1 A SingleBit PseudoParallel Processing Low Oversampling DeltaSigma Modulator Suitable for SDR Wireless Transmitters
"... modulator (DSM) is considered one of the limiting factors toward its employment in today’s highfrequency applications, such as wireless software defined radio (SDR) systems. This paper advances that the critical requirement for DSMs is highfrequency processing and not a high oversampling ratio. A s ..."
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modulator (DSM) is considered one of the limiting factors toward its employment in today’s highfrequency applications, such as wireless software defined radio (SDR) systems. This paper advances that the critical requirement for DSMs is highfrequency processing and not a high oversampling ratio. A singlebit semiparallel processing structure to accomplish the highfrequency processing is proposed in this paper. Using the suggested lowoversampling digital DSM architecture, highspeed, highcomplexity computations, which are normally required for wireless applications, are executed in parallel. This facilitates the design of embedded SDR multistandard transmitters using commercially available digital processors. The most favorable application of the proposed singlebit DSM is to build an RF transmitter that includes a onebit quantifier with twolevel switching power amplifier for both high linearity and high efficiency. Performance analysis was carried out by using MATLAB simulations, which showed a reduction of the oversampling ratio by a factor of 16 (for a baseline oversampling ratio of 256) with the same signal to noise (SNR) ratio. The proposed DSM was also implemented on a fieldprogrammable gate array (FPGA) board and its performance was validated by using a code division multiple access (CDMA) signal. Bandwidth of the output signal was increased four times without increasing the processing frequency. Simultaneously, quality of the output signal remained the same but FPGA resource usage was increased by a factor of three.
RECOVERING SIGNALS FROM LOWPASS DATA 1 Recovering Signals from Lowpass Data
, 907
"... Abstract — The problem of recovering a signal from its low frequency components occurs often in practical applications due to the lowpass behavior of many physical systems. Here we study in detail conditions under which a signal can be determined from its lowfrequency content. We focus on signals i ..."
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Abstract — The problem of recovering a signal from its low frequency components occurs often in practical applications due to the lowpass behavior of many physical systems. Here we study in detail conditions under which a signal can be determined from its lowfrequency content. We focus on signals in shiftinvariant spaces generated by multiple generators. For these signals, we derive necessary conditions on the cutoff frequency of the lowpass filter as well as necessary and sufficient conditions on the generators such that signal recovery is possible. When the lowpass content is not sufficient to determine the signal, we propose appropriate preprocessing that can improve the reconstruction ability. In particular, we show that modulating the signal with one or more mixing functions prior to lowpass filtering, can ensure the recovery of the signal in many cases, and reduces the necessary bandwidth of the filter. Index Terms — Sampling, shiftinvariant spaces, lowpass signals I.
THE REQUIREMENTS FOR THE DEGREE OF
, 2008
"... ii Many emerging applications call for wideband analogtodigital converters and some require mediumtohigh resolution. Incorporating such ADCs allows for shifting as much of the signal processing tasks as possible to the digital domain, where more flexible and programmable circuits are available. ..."
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ii Many emerging applications call for wideband analogtodigital converters and some require mediumtohigh resolution. Incorporating such ADCs allows for shifting as much of the signal processing tasks as possible to the digital domain, where more flexible and programmable circuits are available. However, realizing such ADCs with the existing single stage architectures is very challenging. Therefore, parallel ADC architectures such as timeinterleaved structures are used. Unfortunately, such architectures require highspeed highprecision sampleandhold (S/H) stages that are challenging to implement. In this thesis, a parallel ADC architecture, namely, the frequencytranslating hybrid ADC (FTHADC) is proposed to increase the conversion speed of the ADCs, which is also suitable for applications requiring mediumtohigh resolution ADCs. This architecture addresses the sampling problem by sampling on narrowband baseband subchannels, i.e., sampling is accomplished after splitting the wideband input signals into narrower subbands and frequencytranslating them into baseband where identical narrowband baseband S/Hs