www.gusucode.com > signal 工具箱matlab源码程序 > signal/@dfilt/@latticeallpass/ss.m
function [A,B,C,D] = ss(Hd) %SS Discrete-time filter to state-space conversion. % [A,B,C,D] = SS(Hd) converts discrete-time filter Hd to state-space % representation given by % x(k+1) = A*x(k) + B*u(k) % y(k) = C*x(k) + D*u(k) % where x is the state vector, u is the input vector, and y is the output % vector. % % See also DFILT. % Author(s): R. Losada % Copyright 1988-2002 The MathWorks, Inc. k = Hd.Lattice; [A,B]=statespaceab(Hd); if isempty(k) C = []; D = 1; else C = zeros(1,length(k)); C(end) = 1-abs(k(end)).^2; D = conj(k(end)); end % Force uniformity with empty state matrix. if isempty(A) A = []; B = zeros(0,1); C = zeros(1,0); end