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Analog Electronics for Measuring Systems
book

Analog Electronics for Measuring Systems

by Davide Bucci
May 2017
Intermediate to advanced content levelIntermediate to advanced
180 pages
3h 46m
English
Wiley-ISTE
Content preview from Analog Electronics for Measuring Systems

3Elements of Active Filter Synthesis

3.1. Introduction

One of the most convenient operations in signals is linear filtering. In fact, useful information is conveyed on a certain spectral band and everything outside that band can be considered noise. Filtering it out is a good way to increase overall measurement quality. Furthermore, modern measurement systems often involve a sample and hold circuit, coupled with an analog to digital converter. As sampling is subjected to the aliasing phenomenon, this means that an analog anti-aliasing filter must always be present. In some low-performance applications, the natural low-pass behavior of sensors and amplifiers might be sufficient, but to achieve high performances, a dedicated filtering block becomes mandatory.

Filter design is a huge domain whose surface is barely scratched by this chapter. We want to provide an understanding of the problems and the terminology, as well as a design method for simple active filters.

Figure 3.1 shows the classic design flow for filter design. The first operation is called approximation. It consists of writing down a transfer function H(p) of a two-port network (in the Laplace domain):

where n(p) and g(p) are polynomials (with real coefficients of p, the Laplace variable), such that the response |H(j2πf)| of the filter matches some constraints. Usually, attenuation in some frequency bands is ...

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Publisher Resources

ISBN: 9781786301482Purchase book