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fq2ri

PURPOSE ^

FQ2RI Convert frequency/Q pole/zero representation

SYNOPSIS ^

function ri= fq2ri(f0, Q)

DESCRIPTION ^

 FQ2RI Convert frequency/Q pole/zero representation
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 DESCRIPTION: FQ2RI Convert frequency/Q pole/zero representation into real
              and imaginary conjugate pairs.
              Returns [ri conj(ri)]

 CALL:        ri= fq2ri(f0, Q)

 VERSION:     $Id: fq2ri.m,v 1.3 2008/07/11 17:34:47 ingo Exp $

 HISTORY:     02-04-2007 M Hewitson
                 Creation

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CROSS-REFERENCE INFORMATION ^

This function calls: This function is called by:

SOURCE CODE ^

0001 % FQ2RI Convert frequency/Q pole/zero representation
0002 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0003 %
0004 % DESCRIPTION: FQ2RI Convert frequency/Q pole/zero representation into real
0005 %              and imaginary conjugate pairs.
0006 %              Returns [ri conj(ri)]
0007 %
0008 % CALL:        ri= fq2ri(f0, Q)
0009 %
0010 % VERSION:     $Id: fq2ri.m,v 1.3 2008/07/11 17:34:47 ingo Exp $
0011 %
0012 % HISTORY:     02-04-2007 M Hewitson
0013 %                 Creation
0014 %
0015 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
0016 
0017 function ri= fq2ri(f0, Q)
0018 
0019   if(nargin==0)
0020     disp('usage: ri = fq2ri2(f0, Q)')
0021     return
0022   elseif(nargin==1 || nargin==2 && isnan(Q))
0023     ri = -(1/(2*pi*f0));
0024   elseif(nargin==2 && Q>=0)
0025     if Q < 0.5
0026       warning('!!! Q < 0.5! Splitting to two real poles;')
0027       ri = [-(1/(2*pi*f0)) -(1/(2*pi*f0))];
0028     else
0029       w0  = 2*pi*f0;
0030       G   = 1/(w0*w0);
0031       re  = G.*-w0/(2*Q);
0032       im  = G.*w0*sqrt(4*Q*Q-1)/(2*Q);
0033       tri = complex(re,im);
0034       ri  = [tri; conj(tri)];
0035     end
0036   end
0037

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