1.軟體版本
matlab2021a
2.系統原理
在無線通信中，為了對抗信道衰落和保證傳輸資訊的安全常采用跳頻（Frequency Hopping, FH）通信技術。高斯移頻鍵控（Gauss Frequency Shift Keying, GFSK）具有恒幅包絡、功率譜集中、頻譜較窄等無線通信系統所希望的特性。FH-GFSK則結合了上述兩種技術的優點，是以，在數字通信中得到廣泛應用。本課題采用基于GNU Radio的軟體無線電接收機首先對FH-GFSK信号進行采集，随後對采集到的信号進行分析，最終實作信号的盲解調。通過本課題的研究，旨在加深學生對跳頻通信、高斯移頻鍵控技術的了解，掌握通信信号的分析與處理方法
1.完成5.8GHz頻段的FH-GFSK信号的采集、分析和盲解調。
2.采用基于GNU Radio的軟體無線電接收機對射頻FH-GFSK進行采集。
3.采用Matlab對采集的信号進行跳速和跳頻圖案分析，得到其跳頻圖案。
4.采用Matlab對GFSK信号的高斯濾波參數、調制指數等參數進行估計，用于完成FH-GFSK信号的盲解調。
根據參考文獻可知，GMSK解調結構如下所示：
可參考：https://wenku.baidu.com/view/1631562eb307e87101f69679.html
是以在進行盲估計時候，需要知道fc，和低通濾波器的參數，後面的是固定結構，就不用估計了。
然後題目中講到：
高斯濾波器參數，實際上就是獲得對應的低通濾波器；
然後調制指數的計算公式為：
3.部分源碼
fs = 100e6;
Nfft = 4096;
frameNumber = floor(length(x)/Nfft);
txBlockFFT = zeros(frameNumber,Nfft);
for i = 0:frameNumber-1
i
start = i*Nfft;
txBlockFFT(i+1,:) = fftshift(fft(x(start+1:start+Nfft)));
[maxValue maxIndex(i+1)] = max(abs(txBlockFFT(i+1,:)));
end
fc = 5.8e9;
delta_f = fs/Nfft;
f = delta_f: delta_f: fs;
f = f - fs/2;
%detect vaalid signal
validIndexCount = 1;
validIndex = zeros(1,1);
validIndex(validIndexCount) = 0;
validFrameCount = 0;
axes(handles.axes1);
for i = 1:frameNumber-1
i
if(max(abs(txBlockFFT(i+1,:))> 280))
validFrameCount = validFrameCount + 1;
validFrame(validFrameCount) = i+1;
if(abs(maxIndex(i+1) - validIndex(validIndexCount)) > 40)
validIndexCount = validIndexCount +1;
validIndex(validIndexCount) = maxIndex(i+1) ;
detectFHFc = validIndex(2:end)*fs/Nfft- fs/2;
end
detectFHResult(i+1) = maxIndex(i+1)*fs/Nfft- fs/2+fc;
t = (0:length(detectFHResult)-1)*Nfft/fs;
plot(t,detectFHResult,'c*');
hold on
end
axis([0,0.1983,5.74e9,5.86e9]);
pause(0.001);
end
hold on;
y_label = fc*ones(1,length(detectFHResult));
plot(t,y_label,'r');
ylim([fc-50e6 fc+50e6]);
xlabel('時間s')
ylabel('頻率Hz');
grid on;
ind1 = find(abs(detectFHResult)>0) ;
ind2 = find(detectFHResult==0) ;
detectFHResult(ind2)=[];
flag = [];
for i = 1:length(ind1)-1
if ind1(i+1)-ind1(i) > 20
flag = [flag,i];
end
end
%鎖定頻率點
for i = 1:length(flag)
if i == 1
detectFHResult2(i) = mean(detectFHResult(1:flag(i)));
else
detectFHResult2(i) = mean(detectFHResult(flag(i-1)+1:flag(i)));
end
end
%跳頻周期
for i = 1:length(flag)
if i == 1
ind12(i) = ind1(flag(i)+1)-ind1(1);
else
ind12(i) = ind1(flag(i)+1)-ind1(flag(i-1)+1);
end
end
cycle = floor(mean(ind12)); parameters;
t = (0:Nfft-1)/fs;
t = t';
for i=0:frameNumber-1
start = i*Nfft;
txBlockFFT(i+1,:) = fftshift(fft(x(start+1:start+Nfft)));
end
Avgs = 1000*mean2(abs(txBlockFFT));
%調制指數
%高斯濾波參數估計
indx = 0;
for i=0:frameNumber-100%分幀進行實時參數估計
i
[maxValue,maxIndex(i+1)]= max(abs(txBlockFFT(i+1,:)));
if max(abs(txBlockFFT(i+1,:)))> Avgs
indx = indx + 1;
if(abs(maxIndex(i+1) - validIndex(validIndexCount)) > 40)
validIndexCount = validIndexCount +1;
validIndex(validIndexCount) = maxIndex(i+1) ;
detectFHFc = validIndex(2:end)*fs/Nfft- fs/2;
end
detectFHResult(i+1) = maxIndex(i+1)*fs/Nfft- fs/2+fc;
selectFrameData = txBlockFFT(i+1,:);
[maxValue,maxIndex] = max(abs(selectFrameData));
selectFHFc = maxIndex*fs/Nfft- fs/2;
startIndex = (i+1)*Nfft;
selectRxFrame(i+1,:) = x(startIndex+1:startIndex+Nfft).*(cos(2*pi*selectFHFc*t)-sqrt(-1)*sin(2*pi*selectFHFc*t));
%去除中斷後的直接合并的信号
selectRxFrame2(indx,:)= x(startIndex+1:startIndex+Nfft).*(cos(2*pi*selectFHFc*t)-sqrt(-1)*sin(2*pi*selectFHFc*t));
else
startIndex = (i+1)*Nfft;
selectRxFrame(i+1,:)= x(startIndex+1:startIndex+Nfft);%無信号區域
end
end
axes(handles.axes2);
[R,C] = size(selectRxFrame2);
Rx = reshape(selectRxFrame2',[1,R*C]);
plot(real(Rx),'b');
xlabel('時間s')
grid on;
axis([2000,20000,-1,1]);
%資料還原成原始的一維信号
[R,C] = size(selectRxFrame2);
Rx = reshape(selectRxFrame2',[1,R*C]);
%濾波器估計值
%計算帶寬,通過計算-3db頻譜範圍作為帶寬
[x0,t,ssf,yy] = plotspec(Rx,1/fs);
Y2 = 10*log10(yy/max(yy));
Y3 = Y2(length(Y2)/2:end);
indx = find(Y3>=-3);
ssf2 = ssf(length(ssf)/2:end);
BB = (ssf2(indx(end))-ssf2(indx(1)));
BT = 100*BB/fs;
disp('調制指數');
set(handles.edit2,'string',num2str(BT));
Rfinal = [];
for i = 1:R
i
RR = selectRxFrame2(i,:);
[Isignal_,h] = glpfsignal(real(RR),fs,BT);
[Qsignal_,h] = glpfsignal(imag(RR),fs,BT);
%濾波這塊比較費時，我這裡隻截取一部分進行處理
Isignal = Isignal_(1:length(RR));
Qsignal = Qsignal_(1:length(RR));
%輸出二進制資料
tmps = Isignal.*[diff(Qsignal,1),0] - Qsignal.*[diff(Isignal,1),0];
%做下濾波處理
tmps = tmps-mean(tmps);
w = hamming(128);
tmps = conv(tmps,w);
tmps = tmps-mean(tmps);
Rfinal = [Rfinal,tmps];
end
tmps2= Rfinal>=0;
axes(handles.axes3);
plot(Rfinal)
axis([2000,20000,-2,3]);
axes(handles.axes4);
plot(tmps2)
axis([2000,20000,-1,2]);
disp('跳周期');
cycle
disp('頻率點');
detectFHResult2
fid = fopen('a.txt','wt');
for i = 1:16
fprintf(fid,'%6.2f\n',detectFHResult2(i));
end
fclose(fid);