?clc;?clear;close?all;
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%%?1.輸入?yún)?shù)設置?%%
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%?參數(shù)配置；參數(shù)是如何確定的？？？？？？？？？？？？？？？？？
fs?=?100e6;?????????????????????????????????????%?采樣頻率128MHz；
f?=?72e6;????????????????????????????????????????%?載波頻率1MHz；72M
d_cic?=?8;??%?CIC濾波器抽取率2<=D<=512；
q_cic?=?5;??%?CIC濾波器級數(shù)q
d_fir1?=?4;?????????????????????????????????????%?FIR1濾波器抽取率；?
d_fir2?=?2;?????????????????????????????????????%?FIR2濾波器抽取率；?
%?設置采樣點數(shù)；
N?=?128*100*8*2;???
n?=?0:N-1;
%?生成輸入信號；
x_in?=cos（2*pi*5e3*n/fs）;?%基頻10KHz;????????cos（wt）{w=2*pi*f???t=n/fs}
%x_in_q?=?round（x_in*2^31）/2^31;
x_in_q?=?round（x_in*2^7）/2^7;

%?計算頻率分辨率；
fd?=?fs/N;??????????????????????????????????????%?采樣頻率——fs；采樣點數(shù)——N；??????????????
display（fd）;??
disp（‘Hz‘）;

%?生成加漢寧窗；
w?=?hann（N‘symmetric‘）;?%symmetric??periodic??兩種方式?jīng)]區(qū)別

%?加漢寧窗的傅里葉變換；
fft_x_in?=?fft（x_in_q.*w‘）;%????.*為矩陣點乘
?
%頻譜修正；
fft_x_in?=?fft_x_in（1:N/2+1）/N*4;
A?=?abs（fft_x_in）;???????????????????%abs??求絕對值

%結果顯示；
figure（10）;
subplot（211）;
plot（n/fsx_in）;???%n=0;N-1?N=128*100*8*2
xlabel（‘時間t/s‘）;ylabel（‘基帶信號幅度‘）;grid?on;title（‘基帶信號波形‘）;

f0?=?fs*（0:N/2）/N/1e6;%歸一化??對稱只需要用到一半的點
subplot（212）;
plot（f020*log10（A））;
axis（[0?0.5?-inf?inf]）;
xlabel（‘頻率（MHz）‘）;ylabel（‘功率譜‘）;grid?on;title（‘基帶信號頻譜‘）;
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%%?2.調制?%%
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%?FM_out?=?0.2685*x_in.*cos（2*pi*f*n/fs）+1.6*noise;??????%?基頻1KHz+1.5KHz+5KHz，載頻1M，噪聲Vppn?=?10；
f_carry?=?cos（2*pi*f*n/fs）;??????????????????????????????%?載波頻率?f=72Mhz
f_carry_q?=round（f_carry*2^7）/2^7;???????????????????????%?載頻8位量化（最高位為符號位）round?為取最近的整數(shù)
FM_out?=?x_in_q.*f_carry_q;??????????????????????????????%?基頻1KHz+1.5KHz+5KHz，載頻1M，噪聲Vppn?=?10；
FM_out_noise?=?awgn（FM_out20）;????????????????%y?=?awgn（xsnr）?x信號，snr是信噪比
FM_out?=?0.8537*FM_out/max（FM_out）;??????????????????????%?歸一化，滿刻度量化（為什么要乘上0.8537）
FM_out_q?=?fix（FM_out*2^7）/2^7;????????????????????????%?（fix舍小數(shù)取整）輸入調制信號經(jīng)過16bit的量化

%?加漢寧窗的傅里葉變換；
fft_FM_out?=?fft（FM_out_q.*w‘）;???????

%?頻譜修正；
fft_FM_out?=?fft_FM_out（1:N/2+1）/N*4;
A?=?abs（fft_FM_out）;

%?結果顯示；
figure（21）;
subplot（211）;
plot（n/fsFM_out_q）;
xlabel（‘時間t/s‘）;ylabel（‘調制信號幅度‘）;grid?on;title（‘調制信號波形‘）;

%?subplot（312）;
%?plot（f020*log10（A））;
%?xlabel（‘頻率（MHz）‘）;ylabel（‘功率譜‘）;grid?on;title（‘未修正調制信號頻譜‘）;

subplot（212）;
plot（f020*log10（A））;
axis（[27.8?29.2?-inf?0]）;
xlabel（‘頻率（MHz）‘）;ylabel（‘功率譜‘）;grid?on;title（‘修正調制信號頻譜‘）;

%?生成Modelsim仿真輸入數(shù)據(jù)；
H=FM_out_q*2^15;
%?H=ceil（H）;
fid=fopen（‘ddc_test_in.dat‘‘wt‘）;
%?fprintf（fid‘%4x\n‘H+（H<0）*2^16）;
fprintf（fid‘%4x\n‘H+（H<0）*2^16）;
fclose（fid）;
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%%?3.NCO混頻?%%???
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%?混頻I支路輸出；
FM_out_int?=?floor（

?屬性????????????大小?????日期????時間???名稱
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?????文件???????12487??2014-05-14?11:51??ddc_purechangeone.m