7.1.m

对应不同的a值产生一组矢量来表示高斯脉冲波形

%
% FUNCTION 7.1 : "cp0701_shape_factor_variation"
%
% Effect of shape factor variation on pulse width and 
% ESD of the Gaussian pulse
% The pulse amplitude is set to 'A'
% 'smp' samples of the Gaussian pulse are considered in
% the time interval 'Tmax - Tmin'
%
% The function receives as input:
% 1) the minimum value of the shape factor 'alphamin'
% 2) the increase step 'alphastep'
% 3) the number of values to be investigated
%  'N_alphavalues'
%
% The function plots for each value of alpha the waveform
% and corresponding ESD
%
% Programmed by Luca De Nardis

function cp0701_shape_factor_variation(alphamin,...
    alphastep, N_alphavalues)
% --------------------------------------------
% Step Zero - Input parameters and initialize
% --------------------------------------------

A=1;                           % pulse amplitude [V]
smp=1024;                      % number of samples
Tmin=-4e-9;                    % lower time interval limit
Tmax=4e-9;                     % upper time interval limit
alpha=alphamin;                % initialization of the shape 
                               % factor
t=linspace(Tmin,Tmax,smp);     % initialization of the time
                               % axis
for i=1:N_alphavalues

% -------------------------------------------
% Step One - Pulse waveform in the time domain
% -------------------------------------------

   % pulse waveform definition
   pulse=-A*exp(-2*pi*(t/alpha).^2);
% -------------------------------------------
% Step Two - Analysis in the frequency domain
% -------------------------------------------
   dt=(Tmax-Tmin)/smp;         % sampling period
   fs=1/dt                     % sampling frequency
   N=smp;                      % number of samples (i.e.,
                               % size of the FFT)
df=1/(N*dt);                   % fundamental frequency

X=fft(pulse);                  % double-sided MATLAB
                               % amplitude spectrum
X=X/N;                         % conversion from MATLAB
                               % spectrum to Fourier
                               % spectrum
E=fftshift(abs(X).^2/(df^2));  % double-sided ESD
Ess=2*E((N/2+1):N);            % single-sided ESD

% ---------------------------------
% Step Three - Graphical output
% ---------------------------------

% Time domain representation

   figure(1);
   PT=plot(t,pulse);
   set(PT,'LineWidth',[2]);
   AX=gca;
   set(AX,'FontSize',12);
   T=title('Time domain');
   
   set(T,'FontSize',14);
   X=xlabel('Time [s]');
   set(X,'FontSize',14); 
   Y=ylabel('Amplitude [V]');
   set(Y,'FontSize',14);
   alphabehaviour={'Increasing \alpha'};
     text(0.75e-9,-0.5,alphabehaviour,...
      'BackgroundColor',[1 1 1]);
   axis([-2e-9 2e-9 -1.2 1.2]);
   hold on 

% frequency domain representation

   figure(2);
   positivefrequency=linspace(0,(fs/2),N/2);
   PF=semilogy(positivefrequency,Ess);
   set(PF,'LineWidth',[2]);
   AX=gca;
   set(AX,'FontSize',12);
   T=title('Frequency domain');
   set(T,'FontSize',14);
   X=xlabel('Frequency [Hz]');
   set(X,'FontSize',14);
   Y=ylabel('ESD [(V^2)*sec/Hz]');
   set(Y,'FontSize',14);
   axis([0 20e9 1e-60 1e-10]);
   text(7.5e9, 1e-25, alphabehaviour,...
      'BackgroundColor',[1 1 1]);
   hold on
   
   alpha=alpha+alphastep;% increase of alpha value for
                         % the next step
end