van der Ploeg / Nauta Calibration Techniques in Nyquist A/D Converters

1. Auflage 2006
ISBN: 978-1-4020-4635-3
Verlag: Springer Netherland
Format: PDF
Kopierschutz: 1 - PDF Watermark

E-Book, Englisch, Band 873, 203 Seiten, eBook

Reihe: The Springer International Series in Engineering and Computer Science

Calibration Techniques in Nyquist A/D Converters analyses different A/D-converter architectures with an emphasis on the maximum achievable power efficiency. It is shown that in order to achieve high speed and high accuracy at high power efficiency, calibration is required. Calibration reduces the overall power consumption by using the available digital processing capability to relax the demands on critical power hungry analog components. Several calibration techniques are analyzed. The calibration techniques presented in this book are applicable to other analog-to-digital systems, such as those applied in integrated receivers. Further refinements will allow using analog components with less accuracy, which will then be compensated by digital signal processing. The presented methods allow implementing this without introducing a speed or power penalty.

Zielgruppe

Research

Autoren/Hrsg.

van der Ploeg, Hendrik

Nauta, Bram

Inhaltsverzeichnis

Accuracy, speed and power relation.- A/D converter architecture comparison.- Enhancement techniques for two-step A/D converters.- A 10-bit two-step ADC with analog online calibration.- A 12-bit two-step ADC with mixed-signal chopping and calibration.- A low-power 16-bit three-step ADC for imaging applications.- Conclusions.

Leseproben

Chapter 1 Introduction (p. 1)

1.1 A/D conversion systems

In modern systems, most of the signal processing is performed in the digital domain. Digital circuits have a lower sensitivity to noise and are less susceptible to fluctuations in supply and process variations. Unlike with analog circuits, signal processing in the digital domain offers greater programmability, error correction and storage possibilities.

They are found in many systems that require digital signal processing. This book focuses on A/D converters. A/D converters can be classified into two groups. There are A/D converters with a high accuracy and a low sample rate and A/D converters with a low accuracy and a high sample rate. This is illustrated in figure 1.1.

The first group includes sigma-delta converters for audio, signal transmission and instrumentation systems, while the second group includes video, camera and wide-band signal transmission systems. In order to increase the accuracy or the speed specifications of the A/D converters in both groups more power is required. The A/D converters from the second group of converters are dealt with in this book.

They are found in products like television sets, security cameras, medical imaging devices, instrumentation, etc. The sampling speed required for these applications is generally in excess of 25 MSample/s and the resolution is 10 bits or more. A few examples of these applications are shown in figure 1.2. The position of the A/D converter in such systems is shown in figure 1.3. In this figure, the signal is conditioned in the analog domain before it is applied to the A/D converter.

For example, the A/D converter converts the down-converted radio frequency (RF) antenna signal to the digital domain. In the case of fgure 1.3, the filtering and channel selection is performed in the analog domain. Another example is an analog video signal with an aspect ratio of 4:3, which is converted to the digital domain. In the digital domain a field memory and additional processing is used to resize the video signal to an aspect ratio of 16:9.

A D/A converter converts this signal back to the analog domain to be applied to a display [1]. Similar signal processing is required As shown in figure 1.3, the A/D converters form the connection between the ana- to convert a video signal with a 50 Hz frame rate to a video signal with a 100 Hz frame rate. The performance level should be such that the system is not affected by the imperfections of the data converter.

Its design is therefore extremely important. Because of the trend towards decreasing feature sizes on silicon, it is becoming cheaper to shift analog functions, such as amplifying, filtering and mixing, into the digital domain. This involves shifting the A/D converter towards the input of the system, an extreme example of this is shown in figure 1.4.

In order to shift the A/D converter towards the input of such systems, A/D converters are required with a greater dynamic range and higher sampling speeds because there is less analog signal conditioning.