freq_offset_compensate.m

这个程序主要是实现空时编码的matlab编解码仿真。

function [quad_comp, inphase_comp, theta]=freq_offset_compensate(quad,inphase)
%   
%   
%   Short Theoretical Background for the Function:
%   
%   Compensating for rotation on symbols.
%   Assuming rotation is less than one circle!!!!!!
%   
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     
%%% Function part of simulation for Space-Time
%%% coding project, group Grey-2001.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%   Author: SU
%   Date: 
%   Version: 
%   Revision (Name & Date & Comment):
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

K = 100;            % mean-window-length, nr of symbols

complex_signal_in = complex(inphase, quad);
figure(6), plot(angle(complex_signal_in))
fi = angle(complex_signal_in);
fi = fi(2000:4000);                           % Study only first third part of data if phase-shift is greater than 2*pi.

A = [[1:length(fi)]' ones(length(fi),1)];         % Solving least-square for straight-line equation
y = fi';
x = A\y                                                 % x = A\y, d鋜 x = [k m]'

first_angle = x(2)
end_angle   = x(1)*length(fi)+x(2)

theta       = (end_angle - first_angle)
delta_theta = abs(theta/length(fi))     % Angle-change per symbol.
a = 0:(length(complex_signal_in)-1);
rotation_vector = exp(-j*a*delta_theta);                               % Rotation compensating vector.

complex_signal_out = rotation_vector .* complex_signal_in;
quad_comp = real(complex_signal_out);
inphase_comp = imag(complex_signal_out);