function [snr] = radar_eq(pt, freq, G, sigma, b, NF, L, range)

% 这个程序是计算方程(3.1.14)基本雷达方程

c = 3.0e+8;

lamda = c/freq;

t0 = 290;

num1 = 10*log10(pt*1.0e3*lamda^2) + 2*G + sigma';

num2 = 10*log10(4.0*pi)^3*1.38e-23 * t0*b) + NF +L;

range_db = 40*log10(range*1000);

snr = num1*ones(1, length(range)) - num2-ones(length(sigma),1)*range_db;

figure; plot(range,snr.'); ylabel('SNR/dB'); xlabel('距离/km');