time to sample convert

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majid
majid 2021-7-14
回答： Kothuri 2024-8-23
Hi! how can i convert time vector of the following plot to number of sample?
clear all clc set(0,'defaultlinelinewidth',1) True_range=1000;%Range to target el=1.619*10^(-19);%electron charge pulse_width=10e-9; PRF=10;%pulse per second P_avg=0.4; %Average laser power E_t=P_avg/PRF;%energy per pulse in units of joule sigma_w=2e-9; %standard deviation second theta_t=.01; % divergence beam in radiance theta_r=pi;% Reflection angle prom target tau_atm=1;%atmospheric transmission loss tau_opt=1;%reciever optics transmission rho_t=.1;%target reflection reciever_focal=.1;% reciever focal length delta=1e-4;%physical size of the detectorin the ladar recieverin meters dA=(True_range*delta/reciever_focal)^2;%area of target illuminated by light ap_diameter=.01; Rmin=990; minT=Rmin*2/3e8; Rmax=1010; maxT=Rmax*2/3e8; deltat=sigma_w/10; %sample time to ensure good pulse shape sampling t=minT:deltat:maxT; %range of times over which the return signal is measured P_t=(E_t/(sqrt(2*pi)*sigma_w))*exp(-((t-True_range*2/3e8).^2)/(2*sigma_w^2)); I_target=4*tau_atm*P_t/(pi*(True_range^2)*(theta_t^2)); P_ref=I_target*dA*rho_t; %Reflected power I_reciever=tau_atm*P_ref/(theta_r*True_range^2); %intensity at the aperture P_rec= tau_opt*(ap_diameter^2)*pi*I_reciever/4; %recieved signal power after reciever optics % figure; % plot(t,P_rec) % xlabel('Time (sec)') % ylabel('Prec (watt)') % axis tight quantum_eff=.075; h=6.626e-34; v=3e8/1.55e-6; N=P_rec*deltat*quantum_eff/(h*v);%generated photoelectron figure; plot(t,N) xlabel('Time (sec)') ylabel('photon') title('noisless signal') axis tight
  2 个评论
KSSV
KSSV 2021-7-14
Arrange your code properly.
majid
majid 2021-7-14
oh , I'm sorry.
here the codes:
I want to convert time to sample in the last parameter " signal ".
clear all
clc
set(0,'defaultlinelinewidth',1)
True_range=1000;%Range to target
el=1.619*10^(-19);%electron charge
pulse_width=10e-9;
PRF=10;%pulse per second
P_avg=0.4; %Average laser power
E_t=P_avg/PRF;%energy per pulse in units of joule
sigma_w=2e-9; %standard deviation second
theta_t=.01; % divergence beam in radiance
theta_r=pi;% Reflection angle prom target
tau_atm=1;%atmospheric transmission loss
tau_opt=1;%reciever optics transmission
rho_t=.1;%target reflection
reciever_focal=.1;% reciever focal length
delta=1e-4;%physical size of the detectorin the ladar recieverin meters
dA=(True_range*delta/reciever_focal)^2;%area of target illuminated by light
ap_diameter=.01;
Rmin=990;
minT=Rmin*2/3e8;
Rmax=1010;
maxT=Rmax*2/3e8;
deltat=sigma_w/10; %sample time to ensure good pulse shape sampling
t=minT:deltat:maxT; %range of times over which the return signal is measured
P_t=(E_t/(sqrt(2*pi)*sigma_w))*exp(-((t-True_range*2/3e8).^2)/(2*sigma_w^2));
I_target=4*tau_atm*P_t/(pi*(True_range^2)*(theta_t^2));
P_ref=I_target*dA*rho_t; %Reflected power
I_reciever=tau_atm*P_ref/(theta_r*True_range^2); %intensity at the aperture
P_rec= tau_opt*(ap_diameter^2)*pi*I_reciever/4; %recieved signal power after reciever optics
% figure;
% plot(t,P_rec)
% xlabel('Time (sec)')
% ylabel('Prec (watt)')
% axis tight
quantum_eff=.075;
h=6.626e-34;
v=3e8/1.55e-6;
N=P_rec*deltat*quantum_eff/(h*v);%generated photoelectron
% figure;
% plot(t,N)
% xlabel('Time (sec)')
% ylabel('photon')
% title('noisless signal')
% axis tight
%/////////////////////////////////////////////////
%quantization
A=1; %amplitude of signal
x8=quantBits(N,8,A); %Quantization funcion call
q=2/2^8;
x_8=x8*q;
%/////////////////////////////////////////////////
%shot noise modeled by white noise
SNR=20;
N_shot=awgn(N,SNR,'measured');% white noise adding
%/////////////////////////////////////////////////
M=ones(size(N)); %coherence parameter
x=rand(size(N));
N_speckle=icdf('nbin',x,M,M./(N+M));
%//////////////////////////////////////////////////////////////////////////
kb=1.3806504*10^(-23);
T=300;
C=1e-12;
Q_n_sq=kb*T*C/el;
N_thermal=sqrt(Q_n_sq)*randn(size(N));
%//////////////////////////////////////////////////////////////////////////
S_irr=1000; %watts per square meter per micometer
delta_lam=.001; % bandwidth of reciever micrometer
pbk=S_irr*delta_lam*dA*rho_t*ap_diameter^2/(4*True_range^2); %background power collected by reciever
i_dark=0.75e-9;
N_dark=i_dark*pulse_width/el;
N_b=pbk*pulse_width*quantum_eff*tau_atm*tau_opt/(h*v)+N_dark; %number of photoelectrons from the background
N_back=poissrnd(N_b*ones(size(N)));
%//////////////////////////////////////////////////////////////////////////
sig=sqrt(N.^2+x_8.^2+N_speckle.^2+N_thermal.^2+N_back.^2+N_shot.^2);
signal=(sig-mean(sig));
figure
plot(t.*1000000,signal)
xlabel('Time (microsec)')
ylabel('photon')
title('noisy signal')
axis tight

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回答（1 个）

Kothuri
Kothuri 2024-8-23
Hi Majid,
To convert the time vector to samples in the last parameter "signal", you can
  • Calculate the Number of Samples by determining the length of the time vector “t”.
  • Create a Sample Index Vector that represents sample indices ranging from 1 to the number of samples.
  • Plot the signal Using Sample index vector as the x-axis
% Calculate the number of samples
num_samples = length(t);
% Create a sample index vector
sample_indices = 1:num_samples;
% Plot the noisy signal using sample indices
figure;
plot(sample_indices, signal);
xlabel('Sample Number');
ylabel('Photon Count');
title('Noisy Signal');
axis tight;
By implementing these changes, you can display the signal data in terms of sample numbers.

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