162 lines
5.6 KiB
HTML
162 lines
5.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
|
|
|
|
<!--Converted with LaTeX2HTML 2002-2-1 (1.71)
|
|
original version by: Nikos Drakos, CBLU, University of Leeds
|
|
* revised and updated by: Marcus Hennecke, Ross Moore, Herb Swan
|
|
* with significant contributions from:
|
|
Jens Lippmann, Marek Rouchal, Martin Wilck and others -->
|
|
<HTML>
|
|
<HEAD>
|
|
<TITLE>Band-pass and stop-band filters</TITLE>
|
|
<META NAME="description" CONTENT="Band-pass and stop-band filters">
|
|
<META NAME="keywords" CONTENT="book">
|
|
<META NAME="resource-type" CONTENT="document">
|
|
<META NAME="distribution" CONTENT="global">
|
|
|
|
<META NAME="Generator" CONTENT="LaTeX2HTML v2002-2-1">
|
|
<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">
|
|
|
|
<LINK REL="STYLESHEET" HREF="book.css">
|
|
|
|
<LINK REL="next" HREF="node131.html">
|
|
<LINK REL="previous" HREF="node129.html">
|
|
<LINK REL="up" HREF="node128.html">
|
|
<LINK REL="next" HREF="node131.html">
|
|
</HEAD>
|
|
|
|
<BODY >
|
|
<!--Navigation Panel-->
|
|
<A NAME="tex2html2521"
|
|
HREF="node131.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/next.png"></A>
|
|
<A NAME="tex2html2515"
|
|
HREF="node128.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/up.png"></A>
|
|
<A NAME="tex2html2509"
|
|
HREF="node129.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/prev.png"></A>
|
|
<A NAME="tex2html2517"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/contents.png"></A>
|
|
<A NAME="tex2html2519"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A NAME="tex2html2522"
|
|
HREF="node131.html">Equalizing filters</A>
|
|
<B> Up:</B> <A NAME="tex2html2516"
|
|
HREF="node128.html">Taxonomy of filters</A>
|
|
<B> Previous:</B> <A NAME="tex2html2510"
|
|
HREF="node129.html">Low-pass and high-pass filters</A>
|
|
<B> <A NAME="tex2html2518"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A NAME="tex2html2520"
|
|
HREF="node201.html">Index</A></B>
|
|
<BR>
|
|
<BR>
|
|
<!--End of Navigation Panel-->
|
|
|
|
<H2><A NAME="SECTION001212000000000000000"></A>
|
|
<A NAME="sect8.bandpassdef"></A>
|
|
<BR>
|
|
Band-pass and stop-band filters
|
|
</H2>
|
|
|
|
<P>
|
|
A
|
|
<A NAME="10086"></A><A NAME="10087"></A><I>band-pass filter</I>
|
|
admits frequencies within a given band, rejecting frequencies below it and
|
|
above it. Figure <A HREF="#fig08.03">8.3</A> shows the frequency response of a band-pass
|
|
filter, with the key parameters labelled. A stop-band filter
|
|
does the reverse, rejecting frequencies within the band and letting through
|
|
frequencies outside it.
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A NAME="fig08.03"></A><A NAME="10092"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 8.3:</STRONG>
|
|
Terminology for describing the frequency response of band-pass and
|
|
stop-band filters. The horizontal axis is frequency and the vertical
|
|
axis is gain. A band-pass filter is shown; a stop-band filter would have a
|
|
contiguous stopband surrounded by two passbands.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="491" HEIGHT="326" BORDER="0"
|
|
SRC="img856.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig08.03.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
In practice, a simpler language is often used for describing bandpass filters,
|
|
as shown in Figure <A HREF="#fig08.04">8.4</A>. Here there are only two parameters: a
|
|
<A NAME="10096"></A><I>center frequency</I>
|
|
and a
|
|
<A NAME="10098"></A><I>bandwidth</I>.
|
|
The passband is considered to be the region where the filter has at least half
|
|
the power gain as at the peak (i.e., the gain is within 3 decibels of its
|
|
maximum). The bandwidth is the width, in frequency units, of the passband.
|
|
The center frequency is the point of maximum gain, which is approximately the
|
|
midpoint of the passband.
|
|
|
|
<P>
|
|
|
|
<DIV ALIGN="CENTER"><A NAME="fig08.04"></A><A NAME="10102"></A>
|
|
<TABLE>
|
|
<CAPTION ALIGN="BOTTOM"><STRONG>Figure 8.4:</STRONG>
|
|
A simplified view of a band-pass filter, showing bandwidth and
|
|
center frequency.</CAPTION>
|
|
<TR><TD><IMG
|
|
WIDTH="288" HEIGHT="226" BORDER="0"
|
|
SRC="img857.png"
|
|
ALT="\begin{figure}\psfig{file=figs/fig08.04.ps}\end{figure}"></TD></TR>
|
|
</TABLE>
|
|
</DIV>
|
|
|
|
<P>
|
|
<HR>
|
|
<!--Navigation Panel-->
|
|
<A NAME="tex2html2521"
|
|
HREF="node131.html">
|
|
<IMG WIDTH="37" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="next"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/next.png"></A>
|
|
<A NAME="tex2html2515"
|
|
HREF="node128.html">
|
|
<IMG WIDTH="26" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="up"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/up.png"></A>
|
|
<A NAME="tex2html2509"
|
|
HREF="node129.html">
|
|
<IMG WIDTH="63" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="previous"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/prev.png"></A>
|
|
<A NAME="tex2html2517"
|
|
HREF="node4.html">
|
|
<IMG WIDTH="65" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="contents"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/contents.png"></A>
|
|
<A NAME="tex2html2519"
|
|
HREF="node201.html">
|
|
<IMG WIDTH="43" HEIGHT="24" ALIGN="BOTTOM" BORDER="0" ALT="index"
|
|
SRC="file:/usr/local/share/lib/latex2html/icons/index.png"></A>
|
|
<BR>
|
|
<B> Next:</B> <A NAME="tex2html2522"
|
|
HREF="node131.html">Equalizing filters</A>
|
|
<B> Up:</B> <A NAME="tex2html2516"
|
|
HREF="node128.html">Taxonomy of filters</A>
|
|
<B> Previous:</B> <A NAME="tex2html2510"
|
|
HREF="node129.html">Low-pass and high-pass filters</A>
|
|
<B> <A NAME="tex2html2518"
|
|
HREF="node4.html">Contents</A></B>
|
|
<B> <A NAME="tex2html2520"
|
|
HREF="node201.html">Index</A></B>
|
|
<!--End of Navigation Panel-->
|
|
<ADDRESS>
|
|
Miller Puckette
|
|
2006-12-30
|
|
</ADDRESS>
|
|
</BODY>
|
|
</HTML>
|