MSK信号是一种相位连续、包络恒定并且占用带宽最小的二进制正交2FSK信号。
连续相位调制 http://www.doc88.com/p-51966792119.html
http://www.embedded.com/print/4142719
CPM调制的模型为：
对于MSK GMSK调制，调制指数都是0.5
MSK 的L=1，GMSK的L=3;
http://www.docin.com/p-106846790.html?qq-pf-to=pcqq.c2c
一个简单的GMSK调制和MSK调制的代码。
clc;
clear all;
close all;
% burst = [1 , 1,1,1,1,1,-1,-1,1,1,-1,1,-1,1 , -1,-1,-1,-1,-1,1,1,-1,-1,1,-1,1,-1];
burst = sign(randn(1 , 1000));
% Tb = 3.692e-6;
Tb = 1/19200;
OSR= 16;
BT = 0.3;
Ts = Tb/OSR;
% PREPARING VECTORS FOR DATA PROCESSING
%
PTV = -2*Tb:Ts:2*Tb;
RTV = -Tb/2:Ts:Tb/2;
% GENERATE GAUSSIAN SHAPED PULSE
%
sigma = sqrt(log(2))/(2*pi*BT);
gauss = (1/(sqrt(2*pi)*sigma*Tb))*exp(-PTV.^2/(2*sigma^2*Tb^2));
% GENERATE RECTANGULAR PULSE
%
rect = 1/(2*Tb)*ones(size(RTV));
% CALCULATE RESULTING FREQUENCY PULSE
%
G_TEMP = conv(gauss,rect);
% TRUNCATING THE FUNCTION TO 3xTb
%
G = G_TEMP(OSR+1:4*OSR);
% TRUNCATION IMPLIES THAT INTEGRATING THE FREQUENCY PULSE
% FUNCTION WILL NOT EQUAL 0.5, HENCE THE RE-NORMALIZATION
%
G_FUN = (G-G(1))./(2*sum(G-G(1)));
% CALCULATE RESULTING PHASE PULSE
%
Q_FUN = cumsum(G_FUN);
h = 0.5;
phi(1 : OSR) = 2*pi*h*burst(1) .* Q_FUN(1 : OSR);
phi(1+OSR : 2*OSR) = 2*pi*h*burst(2) .* Q_FUN(1 : OSR) + 2*pi*h*burst(1) .* Q_FUN(1+OSR : 2*OSR);
phi(1+2*OSR : 3*OSR) = 2*pi*h*burst(3) .* Q_FUN(1 : OSR) + 2*pi*h*burst(2) .* Q_FUN(1+OSR : 2*OSR) + ...
2*pi*h*burst(1) .* Q_FUN(1+2*OSR : 3*OSR);
for i = 4 : length(burst)
phi(1+(i-1)*OSR : i*OSR) = 2*pi*h*burst(i) .* Q_FUN(1 : OSR) + 2*pi*h*burst(i-1) .* Q_FUN(1+OSR : 2*OSR) + ...
2*pi*h*burst(i-2) .* Q_FUN(1+2*OSR : 3*OSR) + pi*h*sum(burst(1:i-3));
end
GMSK = exp(j.*phi);
gt = ones(1,OSR);
for i = 1 : OSR
Q_FUN2(i) = sum(gt(1:i));
end
Q_FUN2 = 0.5 / max(Q_FUN2) .* Q_FUN2;
phi2(1 : OSR) = 2*pi*h*burst(1) .* Q_FUN2;
for i = 2 : length(burst)
phi2(1+(i-1)*OSR : i*OSR) = 2*pi*h*burst(i) .* Q_FUN2 + pi*h*sum(burst(1:i-1));
end
MSK = exp(j.*phi2);