mseq.m

北邮《通信原理基于Matlab的计算机仿真》书的源码 m文件 好不容易弄来的

%m序列发生器及其自相关和功率谱密度
clear all; close all;
g = 19;   % G = 10011
state = 8;% state=1000
L = 1000;

%m序列产生
N = 15;
mq = mgen(g,state,L);

%求序列自相关
ms = conv( 1-2*mq, 1-2*mq(15:-1:1) )/N;

figure(1)
subplot(222)
stem(ms(15:end));
axis([0 63 -0.3 1.2]);title('m序列自相关序列')

%m序列构成的信号(矩形脉冲）
N_sample=8;
Tc = 1;
dt = Tc/N_sample;
t = 0:dt:Tc*L-dt;

gt = ones(1,N_sample);
mt = sigexpand(1-2*mq,N_sample);
mt = conv(mt,gt);
figure(1)
subplot(221);
plot(t,mt(1:length(t)));
axis([0 63 -1.2 1.2]);title('m序列矩形成形信号')

st = sigexpand( 1-2*mq(1:15),N_sample );
s = conv(st,gt);
st = s(1:length(st));

rt1 = conv(mt,st(end:-1:1))/(N*N_sample);

subplot(223)
plot(t,rt1(length(st):length(st)+length(t)-1) );
axis([0 63 -0.2 1.2]);title('m序列矩形成形信号的自相关');xlabel('t');

%sinc脉冲
Tc = 1;
dt = Tc/N_sample;
t = -20:dt:20;
gt = sinc(t/Tc);
mt = sigexpand(1-2*mq,N_sample);
mt = conv(mt,gt);

st2 = sigexpand( 1-2*mq(1:15),N_sample );
s2 = conv(st2,gt);
st2 = s2;

rt2 = conv(mt,st2(end:-1:1))/(N*N_sample);

subplot(224);
t1 = -55+dt:dt:Tc*L-dt;
%plot(t,mt(1:length(t)) );
plot(t1,rt2(1:length(t1)));
axis([0 63 -0.5 1.2]);title('m序列sinc成形信号的自相关');xlabel('t');