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Analiza własności metrologicznych przetworników A/D zbudowanych na bazie modulatorów sigma-delta różnych rzędów

Sidor T.

Pomiary Automatyka Kontrola

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2014

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R. 60, nr 2

94--97

PL

W artykule porównano własności metrologiczne przetworników A/D z modulatorami sigma-delta pierwszego i drugiego rzędu stosując analizę w dziedzinie czasu. Wykazano, że przetworniki z modulatorami wyższych rzędów, wykazują w istocie ten sam poziom błędów kwantowania, co przetworniki z modulatorem pierwszego rzędu. Zwrócono również uwagę na istotne niekonsekwencje, pojawiające się w licznych opracowaniach na ten temat, które posługują się analizą w dziedzinie częstotliwości.

EN

In this paper the time domain analysis is used to compare metrological properties of sigma-delta A/D converters with first order modulator and converters with modulators of higher order. Modulators of higher orders are widely advertised for such converters to be used in digital acoustic systems. The paper proves that from the viewpoint of the important metrological property of such converters i.e. the level of quantization error there is no superiority in performance of A/D converters with higher order modulators over converters with modulator of first order. It was confirmed by a simulation experiment, performed using the MICROCAP circuit simulator (Figs. 7 and 8), where the quantization error levels were compared for modulators of first and second order. Moreover, there is pointed out a certain inconsistency present in numerous papers [2, 4, 5] in which the frequency domain analysis is used to explain noise shaping phenomenon. There is no direct digital filtration possible straight at the sigma-delta modulator output and decimation afterwards. In fact both actions are performed by a single counter, which can be described as both, basically decimator and digital filter (Fig.6).

2

Metrological properties of A/D converters utilizing higher order sigma-delta modulators compared with A/D converters with modulators of first order

Sidor T.

Metrology and Measurement Systems

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2014

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Vol. 21, nr 1

37--46

EN

Time domain analysis is used to determine whether A/D converters that employ higher order sigma-delta modulators, widely used in digital acoustic systems, have superior performance over classical synchronous A/D converters with modulators of first order when taking into account their important metrological property which is the magnitude of the quantization error. It is shown that the quantization errors of delta-sigma A/D converters with higher order modulators are exactly on the same level as for converters with a first order modulator.

3

Polyphase Comb Filter Based on Dispatching Input Bit-stream and Interlaying Multiplexer Techniques for Sigma-Delta ADCs

Abdollahvand S., Goes J., Paulino N., Gomes L.

International Journal of Microelectronics and Computer Science

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2012

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Vol. 3, nr 4

152-158

EN

This paper describes a new design approach for implementing a Polyphase Comb Filter (PCF) based on dispatching input bit-stream and interlaying multiplexer techniques. In order to make our solution more energy efficient in comparison with prior art, we start with a detailed analysis of the drawbacks and advantages of the existing classical techniques. A new structure based on a novel SINC3 design is proposed. This new design uses a controller unit to activate one sub-filter in each specific time interval. As a consequence, no input registers and switches are required. Since this decimation filter is working with a single-bit output bit-stream, the required multiplication function can be simply done by using interlaying multiplexers (MUXs). By interlaying different levels of MUXs along with the navigation of the input bit stream we can easily emulate the multiplication operation. The implementation in a Xilinx Spartan3 FPGA demonstrates the feasibility and hardware efficiency of our solution . The proposed new filter architecture can be readily applicable to any Sigma-Delta (ΣΔ) ADC with a single-bit output stream and it requires a reduced number of adders and registers when compared with the state-of-the-art approaches.

4

Current mode comparator design

Pierzchlewski J., Śniatała P., Handkiewicz A.

Elektronika : konstrukcje, technologie, zastosowania

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2008

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Vol. 49, nr 11

167-169

EN

It is known that the inverter is widely used as comparator in voltage mode circuits. However, inverter is an unsatisfactory cell to function as comparator in current mode circuits. The more convenient cell in this situation is so called Traff comparator. The disadvantage of the Traff circuit is its voltage signal output. The paper proposes to add a differential cell to improve properties of the current mode comparator. As a result a novel balanced (fully differential) structure of the current comparator is presented. Theoretical considerations are illustrated in SPICE simulations of circuits realized 0.35 um AMS technology. The usefulness of such comparator in sigma-delta modulator is also shown.

PL

W obwodach pracujących w trybie napięciowym używa się powszechnie inwertera jako komparatora. Jednakże inwerter jest niezadowalającą komórką działającą jako komparator w obwodach pracujących w trybie prądowym. W tej sytuacji bardziej dogodny jest tak zwany komparator Traffa. Ujemną stroną obwodu Traffa jest sygnał napięciowy na jego wyjściu. W pracy zaproponowano dołączenie komórki różnicowej dla poprawienia właściwości komparatora. W efekcie została zaprezentowana nowa, zbalansowana (w pełni różnicowa) struktura komparatora. Rozważania teoretyczne są zilustrowane symulacjami z użyciem programu SPICE obwodu zrealizowanego w technologii 0,35 um AMS. Przedstawiona jest także przydatność tego komparatora w modulatorze sigma-delta.