clear;%指標是signalpower=-185dBW，此時可以進行室內定位；%指標是SNR=-52dB，此時noisepower=-133dBWDopler_bound = 10; %原來是20，為加快運行速度，減少頻率槽數Freq_bin = 500;Fc = 1250000;Length_of_data = 5000;Length_of_fft = 4096;NUM = 5;%50010;Signalpower = -177 %I路信號的功率（dBW）Noisepower = -143 %噪聲的復功率（dBW）Threshold = 1e5;Times_of_ncoh = 40;%變量初始化successcount=0;%在衛星從地平線升起或降落時，用戶速度900m/s時,徑向速度差不多(+ -)10K，fid_ca=fopen('CA_5000.txt','r');CA_samp=fscanf(fid_ca,'%d');%5000點fclose(fid_ca);CA_samp=CA_samp';%本地偽碼FFT:CA_fftCA_local=Average(Length_of_data, Length_of_fft, CA_samp);%plot(CA_local)CA_fft=fft(CA_local);%plot(imag(CA_fft))Idata=ReadIn( ); %把文本Idata全部讀到Idata數組中Qdata=ReadIn( ); %  Idata=Idata';Qdata=Qdata';Idata(1:NUM)=[]; %刪去前NUM個元素Qdata(1:NUM)=[];AMP=sqrt(2*10^(Signalpower/10))   %輸入量為幅度系數，單位相當于（V），%AMP=1e-9，此時signal power=-183dBWDIV_AWGN= 10^(Noisepower/10) %輸入量為高斯白噪聲的方差。DIV_AWGN：在均值means為0時，高斯白噪聲的方差即噪聲的功率單位為（W）for k=1:200 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%    %變量初始化    acq_tag = 0;    coh_count = 1;    ncoh_count = 1;    highdop_index = 1;%初始值    lowdop_index = 0;    %初始化矩陣并清零    R = zeros(20,(2*Dopler_bound+1)*Length_of_fft);    sum_cohe_accum = zeros(Times_of_ncoh,(2*Dopler_bound+1)*Length_of_fft);%相干累積和清零    sum_ncohe_accum = zeros(1,(2*Dopler_bound+1)*Length_of_fft);%非相干累積和清零    ncohe_accum = zeros(1,(2*Dopler_bound+1)*Length_of_fft);       [gr,gi]=MyAwgn(62*5000*20-NUM,DIV_AWGN);%產生隨機高斯白噪聲：    Ich = Idata*AMP+gr;    Qch = Qdata*AMP+gi;            for n=1:Times_of_ncoh %把I和Q轉變成二維數組Isn和Qsn        Isn(n,1:1e5) = Ich(1+(n-1)*1e5 : n*1e5);        Qsn(n,1:1e5) = Qch(1+(n-1)*1e5 : n*1e5);    end;    for ncoh_count=1:Times_of_ncoh%%%進行非相干累積        while coh_count<=20 %%進行相干累積            while (highdop_index <= Dopler_bound) | (lowdop_index>=(-1)*Dopler_bound) %一次5000點搜索                if  lowdop_index >= Dopler_bound*(-1)                    cos_localcarr = LocalCarrier(lowdop_index, Freq_bin, Fc);                    sin_localcarr = LocalCarrier(lowdop_index, Freq_bin, Fc);                    I=Isn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*cos_localcarr-Qsn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*sin_localcarr;                    Q=Isn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*sin_localcarr+Qsn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*cos_localcarr;                    I_short = Average( Length_of_data, Length_of_fft, I);                    Q_short = Average( Length_of_data, Length_of_fft, Q);                    Rev_fft = fft(I_short+i*Q_short); %接收來的信號做fft                    R(coh_count,1+(lowdop_index+Dopler_bound)*Length_of_fft : (lowdop_index+Dopler_bound+1)*Length_of_fft) = ifft(Rev_fft.*conj(CA_fft)); %相關值R，R其實是一個矩陣%                    R_mod(coh_count,1+(lowdop_index+Dopler_bound)*Length_of_fft : (lowdop_index+Dopler_bound+1)*Length_of_fft) = abs(R(coh_count,1+(lowdop_index+Dopler_bound)*Length_of_fft : (lowdop_index+Dopler_bound+1)*Length_of_fft));                end;                if  highdop_index <= Dopler_bound                    cos_localcarr = LocalCarrier(highdop_index, Freq_bin, Fc);                    sin_localcarr = LocalCarrier(highdop_index, Freq_bin, Fc);                    I=Isn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*cos_localcarr-Qsn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*sin_localcarr;                    Q=Isn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*sin_localcarr+Qsn(ncoh_count,1+(coh_count-1)*Length_of_data : coh_count*Length_of_data ).*cos_localcarr;                    I_short = Average( Length_of_data, Length_of_fft, I);                    Q_short = Average( Length_of_data, Length_of_fft, Q);                    Rev_fft = fft(I_short+i*Q_short); %接收來的信號做fft                    R(coh_count,1+(highdop_index+Dopler_bound)*Length_of_fft : (highdop_index+Dopler_bound+1)*Length_of_fft) = ifft(Rev_fft.*conj(CA_fft));    %                 R_mod(coh_count,1+(highdop_index+Dopler_bound)*Length_of_fft : (highdop_index+Dopler_bound+1)*Length_of_fft) = abs(R(coh_count,1+(highdop_index+Dopler_bound)*Length_of_fft : (highdop_index+Dopler_bound+1)*Length_of_fft));                end;                    lowdop_index = lowdop_index-1;                    highdop_index = highdop_index+1;            end; %結束時域搜索頻率，求得單次相關值    %共進行2×Dopler_bound+1次，即 R 實際是 一個21×4096型矩陣    %再進行相干累積20次，即 R 實際是 一個20×21×4096型矩陣    %         [peak,locate]=max(R_mod(coh_count, : ));    %       disp(Threshold);    %       if peak>Threshold  %門限值要科學慎重計算，調試，得到。    %          acq_tag=1;    %          freqbin_index = ceil(locate/Length_of_fft); %向上取整，求出行號即多普勒頻槽號    %          freqbin_index = freqbin_index-Dopler_bound-1;    %          CA_phase = mod(locate,Length_of_fft);       %取模，求出列號即碼相位偏移號    %          CA_phase = Unaverage(Length_of_fft, Length_of_data, CA_phase);    %          CA_phase = CA_phase-1;    %          disp(coh_count);    %          disp(freqbin_index);    %          disp(CA_phase);    %          break;    %       else               sum_cohe_accum(ncoh_count, : ) = sum_cohe_accum(ncoh_count, : ) + R(coh_count, : );               coh_count=coh_count+1;%               if coh_count == 2 & ncoh_count == 1%                   for p=1:21%                    picture(p,:) = R(coh_count, 1+(p-1)*4096 : 4096*p );%                   end;%                   mesh(picture);%               end;%把一次相關結果轉化成picture二維矩陣，畫三維圖    %       end;            end; %結束20ms的20次相干累積%         if  ncoh_count == 1%             for p=1:21%                 picture(p,:) = sum_cohe_accum(1, 1+(p-1)*4096 : 4096*p );%             end;%             mesh(picture);%         end;%把20次相干累積結果轉化成picture二維矩陣，畫三維圖            ncohe_accum( : ) = (abs(sum_cohe_accum(ncoh_count, : )/20)).^2;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%            sum_ncohe_accum( : ) = sum_ncohe_accum( : ) + ncohe_accum( : );%求非相干累積和%                 end;%結束40次非相干累積    for p=1:21        picture(p, : ) = sum_ncohe_accum( 1+(p-1)*4096 : 4096*p );    end;    mesh(picture);    hold on;    [peak, locate] = max(sum_ncohe_accum);    freqbin_index = ceil(locate/Length_of_fft); %向上取整，求出行號即多普勒頻槽號    freqbin_index = freqbin_index-Dopler_bound-1;%freqbin_index取值范圍從 -Dopler_bound，到 +Dopler_bound    CA_phase = mod(locate,Length_of_fft);       %取模，求出列號即碼相位偏移號    CA_phase = Unaverage(Length_of_fft, Length_of_data, CA_phase);    CA_phase = CA_phase-1;    disp(peak);    disp(freqbin_index);    disp(CA_phase);    if (freqbin_index==2) & (CA_phase==(Length_of_data-mod(NUM,Length_of_data))|CA_phase==(Length_of_data-mod(NUM,Length_of_data)-1)|CA_phase==(Length_of_data-mod(NUM,Length_of_data)-2)|CA_phase==(Length_of_data-mod(NUM,Length_of_data)+1))        successcount = successcount+1;        acq_tag = 1;    end;end;        disp(successcount);%     fclose(fid1);%捕獲結束，關掉文本指針%     fclose(fid2);%捕獲結束，關掉文本指針