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author | Daniele Nicolodi <nicolodi@science.unitn.it> |
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date | Mon, 05 Dec 2011 16:20:06 +0100 |
parents | f0afece42f48 |
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% PFALLPS all pass filtering in order to stabilize TF poles and zeros. % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % DESCRIPTION: % % All pass filtering in order to stabilize transfer function poles and % zeros. It inputs a partial fraction expanded discrete model and % outputs a pole-zero minimum phase system % % CALL: % % [resp,np] = pfallps(ir,ip,id,mresp,f) % [resp,np] = pfallps(ir,ip,id,mresp,f,minphase) % [resp,np,nz] = pfallps(ir,ip,id,mresp,f,minphase) % % INPUTS: % % ir: are residues % ip: are poles % id: is direct term % f: is the frequancies vector in (Hz) % minphase: is a flag assuming true (output a minimum phase system) or % false (output a stable non minimum phase system) values. Default, % true % % OUTPUTS: % % resp: is the minimum phase frequency response % np: are new stable poles % nz: are new stable zeros, this will be set only if minphase is set to % false % % NOTE: % % This function make use of signal analysis toolbox functions % % %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % VERSION: $Id: pfallps.m,v 1.7 2008/12/22 18:44:42 luigi Exp $ % % HISTORY: 12-09-2008 L Ferraioli % Creation %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% function varargout = pfallps(ir,ip,id,mresp,f,varargin) % Reshaping [a,b] = size(ir); if a<b ir = ir.'; % reshape as a column vector end [a,b] = size(ip); if a<b ip = ip.'; % reshape as a column vector end [a,b] = size(f); if a<b f = f.'; % reshape as a column vector end [a,b] = size(id); if a > b id = id.'; % reshape as a row id = id(1,:); % taking the first row (the function can handle only simple constant direct terms) end if nargin == 6 minphase = varargin{1}; else minphase = false; end %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% % stabilizing poles sp = p; unst = real(sp) > 0; sp(unst) = -1*conj(sp(unst)); [Na,Nb] = size(r); for nn = 1:Nb s = 1i.*2.*pi.*f; pp = p(unst); psp = sp(unst); for ii = 1:length(s) nterm = 1; for jj = 1:length(sp(unst)) nterm = nterm.*(s(ii)-pp(jj))./(s(ii)-psp(jj)); end phs(ii,1) = angle(nterm); end resp(:,nn) = mresp(:,nn).*(cos(phs)+1i.*sin(phs)); % output stable poles np(:,nn) = sp; if minphase % finding zeros [num,den] = residue(r,p,d); zrs = roots(num); % stabilizing zeros szrs = zrs; zunst = abs(zrs) > 1; szrs(zunst) = 1./conj(zrs(zunst)); zzrs = zrs(zunst); zszrs = szrs(zunst); for ii = 1:length(s) nterm = 1; for jj = 1:length(szrs(zunst)) nterm = nterm.*(s(ii)-zszrs(jj))./(s(ii)-zzrs(jj)); end zphs(ii,1) = angle(nterm); end resp(:,nn) = resp(:,nn).*(cos(zphs)+1i.*sin(zphs)); % output stable zeros nz(:,nn) = szrs; end end % output if nargout == 1 varargout{1} = resp; elseif nargout == 2 varargout{1} = resp; varargout{2} = np; elseif (nargout == 3) && minphase varargout{1} = resp; varargout{2} = np; varargout{3} = nz; else error('Too many output arguments!') end end