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−% GETDC get the DC gain factor for a pole-zero model
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−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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−%
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−% DESCRIPTION
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−% 
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−% A zpk model in matlab notation is an object of the type:
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−% 
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−%         (s-z1)...(s-zN)
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−% zpk = k*----------------
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−%         (s-p1)...(s-pn)
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−% 
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−% the zero-frequency-gain (zfg) or DC gain of this object is obtained by
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−% the equation, for s = 0.
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−% LTPDA pzmodels are constructed by poles, zeros and DC gain. This means
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−% that the value stored in the 'gain' field of the model is the dc gain!
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−% This function calculate k.
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−% 
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−% CALL:
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−% 
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−%     dc = getdc(z,p,k)
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−% 
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−% INPUT:
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−% 
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−%     z: zeros
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−%     p: poles
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−%     k: gain coefficient
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−%       
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−% 
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−% OUTPUT:
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−% 
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−%     dc: dc gain of the model 
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−% 
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−% NOTE:
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−% 
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−%     
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−% 
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−%
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−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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−% VERSION: $Id: getdc.m,v 1.2 2010/02/22 15:14:17 luigi Exp $
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−%
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−% HISTORY:     08-10-2008 L Ferraioli
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−%                 Creation
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−%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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−function dc = getdc(z,p,k)
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−
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−zrs = prod(-1*z);
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−pls = prod(-1*p);
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−
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−dc = k*zrs/pls;
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−
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−end
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