www.pudn.com > minSNRrequired.zip > minSNRrequired.m, change:2003-06-25,size:1318b


% Use this program to reproduce Fig. 1.13 of text. 
close all 
clear all 
pt = 1.e+6; % peak power in Watts 
freq = 5.6e+9; % radar operating frequency in Hz 
g = 40.0; % antenna gain in dB 
sigma = 0.1; % radar cross section in m squared 
te =300.0; % effective noise temperature in Kelvins 
nf = 5.0; %noise figure in dB 
loss = 6.0; % radar losses in dB 
range = [75e3,100e3,150e3]; % three range values 
snr_db = linspace(5,20,200); % SNR values from 5 dB to 20 dB 200 points 
snr = 10.^(0.1.*snr_db); % convert snr into base 10 
gain = 10^(0.1*g); %convert antenna gain into base 10 
loss = 10^(0.1*loss); % convert losses into base 10 
F = 10^(0.1*nf); % convert noise figure into base 10 
lambda = 3.e8 / freq; % compute wavelength 
% Implement Eq.(1.57) 
den = pt * gain * gain * sigma * lambda^2; 
num1 = (4*pi)^3 * 1.38e-23 * te * F * loss * range(1)^4 .* snr; 
num2 = (4*pi)^3 * 1.38e-23 * te * F * loss * range(2)^4 .* snr; 
num3 = (4*pi)^3 * 1.38e-23 * te * F * loss * range(3)^4 .* snr; 
tau1 = num1 ./ den ; 
tau2 = num2 ./ den; 
tau3 = num3 ./ den; 
% plot tau versus snr 
figure(1) 
semilogy(snr_db,1e6*tau1,'k',snr_db,1e6*tau2,'k -.',snr_db,1e6*tau3,'k:') 
grid 
legend('R = 75 Km','R = 100 Km','R = 150 Km') 
xlabel ('Minimum required SNR - dB'); 
ylabel ('\tau (pulse width) in \mu sec');