givens.m

数字通信第四版原书的例程

function g = givens(x,y)
%GIVENS	Givens rotation matrix.
%	G = GIVENS(x,y) returns the complex Givens rotation matrix
%
%	    | c       s |                  | x |     | r | 
%	G = |           |   such that  G * |   |  =  |   |
%           |-conj(s) c |                  | y |     | 0 |
%	                                
%	where c is real, s is complex, and c^2 + |s|^2 = 1. 
 
%	Copyright (c) 1986-93 by The MathWorks, Inc.

absx = abs(x);
if absx == 0.0
	c = 0.0; s = 1.0;
else
	nrm = norm([x y]);
	c = absx/nrm;
	s = x/absx*(conj(y)/nrm);
end
g = [c s;-conj(s) c];