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diff --git a/macros/latc2tf.sci b/macros/latc2tf.sci new file mode 100644 index 0000000..fb19e6d --- /dev/null +++ b/macros/latc2tf.sci @@ -0,0 +1,225 @@ +function [num,den] = latc2tf(k,varargin) + // Convert lattice filter parameters to transfer function coefficients + // + // + // Calling sequence + // [num,den] = latc2tf(k,v) + // [num,den] = latc2tf(k,'iiroption') + // num = latc2tf(k,'firoption') + // + // + // Description + // [num,den] = latc2tf(k,v) + // Finds the transfer function of the IIR filter from the lattice + // coefficients k and ladder coefficients v. + // [num,den] = latc2tf(k,'iiroption') + // Finds the transfer function of the allpass or allpole (specified by + // the iiroption flag) IIR filter. + // num = latc2tf(k,'firoption') + // Finds the transfer function of the FIR filter from the lattice + // coefficients k. The firoption flag specifies the type of the FIR + // filter (can be 'min, 'max', or 'FIR') + // + // Parameters: + // k - double - vector + // Lattice coefficients + // Lattice coefficients for FIR/IIR filter. Can be real or complex. + // v - double - vector + // Ladder coefficients + // Ladder coefficients for IIR filters. Can be real or complex. + // iiroption - string flag - 'allpole', or 'allpass' + // Specification of the type if IIR filter + // firoption - string flag - 'min', 'max', or 'FIR' (default) + // Speficication of the type of FIR filter + // + // Examples + // 1) FIR filter + // k1 = [1/2 1/2 1/4]; + // [num1,den1] = latc2tf(k1); + // + // See also + // latcfilt | tf2latc + // + // References + // [1] J.G. Proakis, D.G. Manolakis, Digital Signal Processing, + // 3rd ed., Prentice Hall, N.J., 1996, Chapter 7. + // [2] S. K. Mitra, Digital Signal Processing, A Computer + // Based Approach, McGraw-Hill, N.Y., 1998, Chapter 6. + // + // Authors + // Ayush Baid + + + [numOutArgs,numInArgs] = argn(0); + +// ** Check on number of input arguments ** + if numOutArgs<1 | numOutArgs>2 then + msg = "cummin: Wrong number of output argument; 1-2 expected"; + error(78,msg); + end + + if numInArgs<1 | numInArgs>2 then + msg = "cummin: Wrong number of input argument; 1-2 expected"; + error(77,msg); + end + + +// ** Parsing the input arguments ** + +// 1) k: +// must be a vector +// can be real or complex valued, (negative values allowed) + + // checking data type + if ~(type(k)==1 | type(k)==8) then + msg = "latc2tf: Wrong type for argument #1 (k); Real or complex vector expected"; + error(53,msg); + end + + // checking the dimensions (must be a vector) + if ~(size(k,1)==1 | size(k,2)==1) then + msg = "latc2tf: Wrong type for argument #1 (k); Real or complex vector expected"; + error(53,msg); + end + // convert to column vector + if size(k,1)==1 then + k = k(:); + end + + L = length(varargin); +// Parsing the 2nd argument + if L>=1 then + arg2 = varargin(1); + // string check + if type(arg2)==10 then + if strcmpi(arg2,'FIR')==0 then + [num,den] = latc2tf_fir(k,2); + elseif strcmpi(arg2,'min')==0 then + [num,den] = latc2tf_fir(k,0); + elseif strcmpi(arg2,'max')==0 then + [num,den] = latc2tf_fir(k,1); + elseif strcmpi(arg2,'allpole')==0 then + [num,den] = latc2tf_iir2(k,1); + elseif strcmpi(arg2,'allpass')==0 then + [num,den] = latc2tf_iir1(k); + else + msg = "latc2tf: Wrong value for argument #2 (string flag) "; + error(53,msg); + end + elseif (type(arg2)==1 | type(arg2)==8) then + // arg2 is ladder coefficients + + // check for vector input + if ~(size(arg2,1)==1 | size(arg2,2)==1) then + msg = "latc2tf: Wrong type for argument #2 (v); Real or complex vector expected"; + error(53,msg); + end + + // convert to column vector + if size(arg2,1)==1 then + arg2 = arg2(:); + end + + [num,den] = latc2tf_iir2(k,arg2); + + else + msg = "latc2tf: Wrong type for argument #2; Real or complex vector" + ... + "(ladder coeffs k) or string flag expected"; + error(53,msg); + end + else + [num,den] = latc2tf_fir(k,2); + end + + num = num'; + den = den'; + +endfunction + +function [num,den] = latc2tf_fir(k,option) + // latc2tf for FIR filters + // Input Arguments + // k: lattice coefficients + // option: 0 for min-phase (default), 1 for max-phase; 2 for fir + + if isempty(k) then + num = 1; + den = 1; + return + end + + den = 1; + + p = length(k); + num = 1; + + for j=2:p+1 + num = [num; 0] + k(j-1)*[0; conj(num($:-1:1,:))]; + end + + if option==1 then + num = conj(num($:-1:1)); + end + + +endfunction + +function [num,den] = latc2tf_iir1(k) + // for all pass IIR filters + + if isempty(k) then + num = 1; + den = 1; + return + end + + p = length(k); + den = 1; + + for j=2:p+1 + den = [den; 0] + k(j-1)*[0; conj(den($:-1:1,:))]; + end + + num = conj(den($:-1:1)); + + +endfunction + + +function [num,den] = latc2tf_iir2(k,v) + // for allpole and general IIR fitlers + if isempty(k) & isempty(v) then + num = []; + den = []; + elseif isempty(k) & length(v)==1 then + num = v; + den = 1; + else + // k is a column vector + M = size(k,1)+1; + + // pad v with appropriate number of zeros + l_v = size(v,1); + diff = M - l_v; + if diff>0 then + v = [v; zeros(diff,1)]; + elseif diff<0 then + k = [k; zeros(-diff,1)]; + end + + + p = length(k); + den = 1; + + for j=2:p+1 + den = [den; 0] + k(j-1)*[0; conj(den($:-1:1,:))]; + end + + exec('rlevinson.sci',-1); + + [r,temp] = rlevinson(den,1); + + num = (temp*v); + end + +endfunction |