function X = sign_mnare(A,B,C,D)
% X=SIGN_MNARE(A,B,C,D) solves the M-NARE C + XA + DX - XBX = 0
% by means of the matrix sign function
%    A, B, C, D: matrix coefficients
%    X : solution of the M-NARE
[n,m] = size(B);
H = [A,-B;-C,-D];
W = matrix_sign(H) - eye(m+n);
X = -W(1:m+n,n+1:n+m)\W(1:m+n,1:n);