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potsband

PURPOSE ^

POTSBAND Design filter for 300-3400 telephone bandwidth [B,A]=(FS)

SYNOPSIS ^

function [b,a]=potsband(fs)

DESCRIPTION ^

POTSBAND Design filter for 300-3400 telephone bandwidth [B,A]=(FS)

Input: FS=sample frequency in Hz

Output: B/A is a discrete time bandpass filter with a passband gain of 1

The filter meets the specifications of G.151 for any sample frequency
and has a gain of -3dB at the passband edges.

CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 function [b,a]=potsband(fs)
0002 %POTSBAND Design filter for 300-3400 telephone bandwidth [B,A]=(FS)
0003 %
0004 %Input: FS=sample frequency in Hz
0005 %
0006 %Output: B/A is a discrete time bandpass filter with a passband gain of 1
0007 %
0008 %The filter meets the specifications of G.151 for any sample frequency
0009 %and has a gain of -3dB at the passband edges.
0010 
0011 
0012 %      Copyright (C) Mike Brookes 1998
0013 %      Version: $Id: potsband.m 713 2011-10-16 14:45:43Z dmb $
0014 %
0015 %   VOICEBOX is a MATLAB toolbox for speech processing.
0016 %   Home page: http://www.ee.ic.ac.uk/hp/staff/dmb/voicebox/voicebox.html
0017 %
0018 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0019 %   This program is free software; you can redistribute it and/or modify
0020 %   it under the terms of the GNU General Public License as published by
0021 %   the Free Software Foundation; either version 2 of the License, or
0022 %   (at your option) any later version.
0023 %
0024 %   This program is distributed in the hope that it will be useful,
0025 %   but WITHOUT ANY WARRANTY; without even the implied warranty of
0026 %   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
0027 %   GNU General Public License for more details.
0028 %
0029 %   You can obtain a copy of the GNU General Public License from
0030 %   http://www.gnu.org/copyleft/gpl.html or by writing to
0031 %   Free Software Foundation, Inc.,675 Mass Ave, Cambridge, MA 02139, USA.
0032 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0033 
0034 szp=[0.19892796195357i; -0.48623571568937+0.86535995266875i]; 
0035 szp=[[0; -0.97247143137874] szp conj(szp)];
0036 % s-plane zeros and poles of high pass 3'rd order chebychev2 filter with -3dB at w=1
0037 zl=2./(1-szp*tan(300*pi/fs))-1;
0038 al=real(poly(zl(2,:)));
0039 bl=real(poly(zl(1,:)));
0040 sw=[1;-1;1;-1];
0041 bl=bl*(al*sw)/(bl*sw);
0042 zh=2./(szp/tan(3400*pi/fs)-1)+1;
0043 ah=real(poly(zh(2,:)));
0044 bh=real(poly(zh(1,:)));
0045 bh=bh*sum(ah)/sum(bh);
0046 b=conv(bh,bl);
0047 a=conv(ah,al);

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