就是最簡單的實現乙個2fsk，先不管這種調製方法的性質
其實就是太懶了不想學
附：rb=100;%設定碼元速率sample=randbinary(n);%生成隨機二進位制序列
%設定傳送波形引數
f1=8000;
f0=12000;
%傳送波形取樣
fs=48000;
send=modulation_2fsk(sample,[f0 f1],rb,fs);
%傳送sound(send,fs);
plot(send);
自定義函式說明：
產生隨機二進位制序列
對單極性不歸零序列進行2fsk調製function [ seq ] = randbinary( n )% 輸入需要生成序列的長度n
% 產生乙個隨機01序列，長度為n
%% 如生成乙個長度為1000的隨機二進位制序列
% sample=randbinary(1000);
seq=zeros(1,n);
for i=1:n
ele=ceil(rand()*10);
seq(i)=mod(ele,2);
endend
採用鍵控法，碼元為1或0時將傳送其對映的波形
然後是對接收訊號進行解調.以下為解調的超理想模式，通道完全無雜訊無衰減！其實根本沒傳輸function [ send ] = modulation_2fsk( sample,f,rb,fs )% 2fsk調製
% 輸入待調製的單極性不歸零序列sample和碼元速率rb
% 傳送頻率[f0 f1]
tb=1/rb;
ts=1/fs;
temp=[0];
send=[0];
n=length(sample);
for i=1:n
temp=i*tb:ts:(i+1)*tb-ts/10;
if sample(i)
send=[send cos(2*pi*f(2)*temp)];
else
send=[send cos(2*pi*f(1)*temp)];
endend
send=send(2:end);
end
因為沒有雜訊不用提取載波，只要對訊號平方在通過lpf即可恢復序列
在解調的過程中，我們要注意由於通道的隨機衰減，可能導致針對某部分頻譜分量的大量衰減，從而不能分辨.為了應對這種情況,我們就需要對經過lpf後的訊號進行歸一化,從而消除因幅度不同而導致的誤差.不能在接收訊號後就進行歸一化,因為訊號中只有部分頻率分量是衰減的,對整個訊號進行歸一化後並不能使衰減訊號恢復到正常值.function [ ] = demodulation_2fsk( rcv,f,fs )% 2fsk解調函式
% 輸入接收訊號rcv和傳送頻率[f0 f1]
% fs為接收訊號的取樣頻率
% 輸出恢復01序列(暫無)，顯示抽樣判決前波形
ts=1/fs;
len=length(rcv);
t=0:ts:(len-1)*ts;
%恢復載波
aid1=cos(2*pi*f(2)*t);
aid0=cos(2*pi*f(1)*t);
%定義濾波器(fpass=500,fstop=2k)
lpf=[-0.000155833996394978,-8.13831647659670e-05,-9.20002718367755e-05,-9.34081381696587e-05,-8.07905288388760e-05,-4.82295684201173e-05,1.10503665725242e-05,0.000104811978995989,0.000241591960167609,0.000430822839276432,0.000682264219483239,0.00100598263039256,0.00141205216632109,0.00191075149567522,0.00251102822992922,0.00322157539693270,0.00404950826762152,0.00500032696122431,0.00607774423655064,0.00728301069263170,0.00861503729572713,0.0100699084385198,0.0116408437704915,0.0133180094004704,0.0150886733499124,0.0169371703821178,0.0188450158385386,0.0207913578208965,0.0227530878451301,0.0247053521313381,0.0266220811202588,0.0284763137354778,0.0302410586230369,0.0318896464873665,0.0333964895832343,0.0347376010424772,0.0358912330554356,0.0368383387237662,0.0375630659622750,0.0380532056874610,0.0383003706934961,0.0383003706934961,0.0380532056874610,0.0375630659622750,0.0368383387237662,0.0358912330554356,0.0347376010424772,0.0333964895832343,0.0318896464873665,0.0302410586230369,0.0284763137354778,0.0266220811202588,0.0247053521313381,0.0227530878451301,0.0207913578208965,0.0188450158385386,0.0169371703821178,0.0150886733499124,0.0133180094004704,0.0116408437704915,0.0100699084385198,0.00861503729572713,0.00728301069263170,0.00607774423655064,0.00500032696122431,0.00404950826762152,0.00322157539693270,0.00251102822992922,0.00191075149567522,0.00141205216632109,0.00100598263039256,0.000682264219483239,0.000430822839276432,0.000241591960167609,0.000104811978995989,1.10503665725242e-05,-4.82295684201173e-05,-8.07905288388760e-05,-9.34081381696587e-05,-9.20002718367755e-05,-8.13831647659670e-05,-0.000155833996394978];
%濾除高頻部分，保留低頻分量
rcv1=filter(lpf,1,rcv.*aid1);
rcv0=filter(lpf,1,rcv.*aid0);
%歸一化
rcv1=rcv1/max(abs(rcv1));
rcv0=rcv0/max(abs(rcv0));
figure
plot(t,abs(rcv1),'-r');
grid on
hold on
plot(t,abs(rcv0),'-g');
title('接受恢復');xlabel('秒/s');
legend('1接收','0接收')
end
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