clc,clear all,close all;

%%%(1111)畫出信號的時域波形
T=0.002*10^(-9);                      %抽樣時間間隔為0.001ns
t=0:T:10^(-9);                      %t從0到1ns
E=1;                                  %定義個參數 
tao=0.11*10^(-9);
tc=0.5*10^(-9);                       
wt=sqrt(E)*sqrt(8/3/tao)*(1-4*pi*((t-tc)/tao).^2).*exp(-2*pi*((t-tc)/tao).^2);     %構造wt，注意這里t是矢量，要用有關矢量的運算符號
%figure(1);
%plot(t,wt);
%xlabel('Time (ns)');
%ylabel('Amplitude');
%title('the time domain undee');

%%%(22222)畫出信號頻譜%%%%%%%%%%%%%%%%%%%%%%%
N=length(wt);
WK=fft(wt);
WK1=10^(-4.13)*abs(WK)/max(abs(WK));
WK2=10*log10(WK1);
f=[-N/2:1:N/2]/T/N;
figure(2);
plot(f/e9,fftshift(wt));
grid;
xlabel('Frequency (GHz)');
ylabel('FIRP Emission Level (dbm)');
title('the frequency domain undee');
axis([0 12*10^11]);