matlab频谱图例⼦_Matlab实例：频谱、功率谱和功率谱密度
计算
本实例以⾼斯信号为例，计算幅度谱、相位谱、双边功率谱、双边功率谱密度、单边功率谱、单边功率谱密度。⾼斯信号的半波全宽FWHM=50ps，中⼼点位于2.5ns处。
MATLAB程序代码：
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%作者：yoyoba
%Email：stuyou@126
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clc;
clear;
FWHM=50e-12;
%⾼斯信号FWHM宽度，为50ps
time_window=100*FWHM;
%⾼斯信号的采样窗⼝宽度，该值决定了傅⾥叶变换后的频率分辨率
Ns=2048;
%采样点
dt=time_window/(Ns-1);
%采样时间间隔
t=0:dt:time_window;
%采样时间
gauss_time=exp(-0.5*(2*sqrt(2*log(2))*(t-2.5e-9)/FWHM).^2);
%⾼斯脉冲，中⼼位于2.5ns处。
plot(t*1e+9,gauss_time,'linewidth',2.5);
xlabel('Time/ns');
ylabel('Amplitude/V');
title('Gauss pulse');
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matlab傅里叶变换的幅度谱和相位谱%以下计算双边谱、双边功率谱、双边功率谱密度
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gauss_spec=fftshift(fft(ifftshift(gauss_time)));
%傅⾥叶变换，并且进⾏fftshift移位操作。
gauss_spec=gauss_spec/Ns;
%求实际的幅度值；
df=1/time_window;
%频率分辨率
k=floor(-(Ns-1)/2
Ns-1)/2), double_f=k*df;
%双边频谱对应的频点
figure;%幅度谱
plot(double_f*1e-9,abs(gauss_spec),'linewidth',2.5);
xlabel('Frequency/GHz');
ylabel('Amplitude/V');
title('double Amplitude spectrum');
figure;%相位谱
plot(double_f*1e-9,angle(gauss_spec),'linewidth',2.5);
xlabel('Frequency/GHz');
ylabel('Phase/rad');
title('double Phase spectrum');
figure;%功率谱
double_power_spec_W=abs(gauss_spec).^2;
%双边功率谱，单位W;
double_power_spec_mW=double_power_spec_W*1e+3;
%双边功率谱，单位mW;
double_power_spec_dBm=10*log10(double_power_spec_mW);
%双边功率谱，单位dBm;
plot(double_f*1e-9,double_power_spec_dBm,'linewidth',2.5);
xlabel('Frequency/GHz');
ylabel('Power/dBm');
title('double Power spectrum');
figure;%功率谱密度
double_power_specD_W=abs(gauss_spec).^2/(df);
%双边功率谱密度，单位W/Hz
double_power_specD_mW=double_power_specD_W*1e+3;
%双边功率谱密度，单位mW/Hz
double_power_specD_dBm=10*log10(double_power_specD_mW); %双边功率谱密度，单位dBm/Hz
plot(double_f*1e-9,double_power_specD_dBm,'linewidth',2.5); xlabel('Frequency/GHz');
ylabel('Power/(dBm/Hz)');
title('double power spectrum Density');
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%以下计算单边谱、单边功率谱及单边功率谱密度
%================
gauss_spec=fft(ifftshift(gauss_time));
%计算单边谱⽆需fftshift
gauss_spec=gauss_spec/Ns;
%计算真实的幅度值
single_gauss_spec=gauss_spec(1:floor(Ns/2));
single_f=(0:floor(Ns/2)-1)*df;
figure;%幅度谱
plot(single_f*1e-9,abs(single_gauss_spec),'linewidth',2.5);
xlabel('Frequency/GHz');
ylabel('Amplitude/V');
title('single Amplitude spectrum');
figure;%相位谱
plot(single_f*1e-9,angle(single_gauss_spec),'linewidth',2.5); xlabel('Frequency/GHz');
ylabel('Phase/rad');
title('single Phase spectrum');
figure;%功率谱
double_power_spec_W=abs(gauss_spec).^2;
single_power_spec_W=2*double_power_spec_W(1:floor(Ns/2)); %单边功率谱，单位W
single_power_spec_mW=single_power_spec_W*1e+3;
%单边功率谱，单位mW;
single_power_spec_dBm=10*log10(single_power_spec_mW);
%双边功率谱，单位dBm;
plot(single_f*1e-9,single_power_spec_dBm,'linewidth',2.5); xlabel('Frequency/GHz');
ylabel('Power/dBm');
title('single Power spectrum');
figure;%功率谱密度
double_power_specD_W=abs(gauss_spec).^2/(df);
single_power_specD_W=2*double_power_specD_W(1:floor(Ns/2));
%单边功率谱密度，单位W/Hz
single_power_specD_mW=single_power_specD_W*1e+3;
%单边功率谱密度，单位mW/Hz
single_power_specD_dBm=10*log10(single_power_specD_mW);
%单边功率谱密度，单位dBm/Hz
plot(single_f*1e-9,single_power_specD_mW,'linewidth',2.5);
xlabel('Frequency/GHz');
ylabel('Power/(dBm/Hz)');
title('single power spectrum density');
运⾏结果....全⽂地址：www.jishulink/content/post/340355

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