clutter_rcs.m
上传用户:szahd2008
上传日期:2020-09-25
资源大小:1275k
文件大小:2k
- function [sigmaC,CNR] = clutter_rcs(sigma0, thetaE, thetaA, SL, range, hr, ht, pt, f0,...
- b, t0, f, l,ant_id)
- % This function calculates the clutter RCS and the CNR for a ground based radar.
- clight = 3.e8; % speed of light in meters per second
- lambda = clight /f0;
- thetaA_deg = thetaA;
- thetaE_deg = thetaE;
- thetaA = thetaA_deg * pi /180; % antenna azimuth beamwidth in radians
- thetaE = thetaE_deg * pi /180.; % antenna elevation beamwidth in radians
- re = 6371000; % earth radius in meter
- rh = sqrt(8.0*hr*re/3.); % range to horizon in meters
- SLv = 10.0^(SL/10); % radar rms sidelobes in volts
- sigma0v = 10.0^(sigma0/10); % clutter backscatter coefficient
- tau = 1/b; % pulse width
- deltar = clight * tau / 2.; % range resolution for unmodulated pulse
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- range_m = 1000 .* range; % range in meters
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- thetar = asin(hr ./ range_m);
- thetae = asin((ht-hr) ./ range_m);
- propag_atten = 1. + ((range_m ./ rh).^4); % propagation attenuation due to round earth
- Rg = range_m .* cos(thetar);
- deltaRg = deltar .* cos(thetar);
- theta_sum = thetae + thetar;
- % use sinc^2 antenna pattern when ant_id=1
- % use Gaussian antenna pattern when ant_id=2
- if(ant_id ==1) % use sinc^2 antenna pattern
- ant_arg = (2.78 * theta_sum ) ./ (pi*thetaE);
- gain = (sinc(ant_arg)).^2;
- else
- gain = exp(-2.776 .*(theta_sum./thetaE).^2);
- end
- % compute sigmac
- sigmac = (sigma0v .* Rg .* deltaRg) .* (pi * SLv * SLv + thetaA .* gain.^2) ./ propag_atten;
- sigmaC = 10*log10(sigmac);
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- figure(1)
- plot(range, sigmaC)
- grid
- xlabel('Slant Range in Km')
- ylabel('Clutter RCS in dBsm')
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- % Calculate CNR
- pt = pt * 1000;
- g = 26000 / (thetaA_deg*thetaE_deg); % antenna gain
- F = 10.^(f/10); % noise figure is 6 dB
- Lt = 10.^(l/10); % total radar losses 13 dB
- k = 1.38e-23; % Boltzman抯 constant
- T0 = t0; % noise temperature 290K
- argnumC = 10*log10(pt*g*g*lambda*lambda*tau .* sigmac);
- argdem = 10*log10(((4*pi)^3)*k*T0*Lt*F .*(range_m).^4);
- CNR = argnumC - argdem;
- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
- figure(2)
- plot(range, CNR,'r')
- grid
- xlabel('Slant Range in Km')
- ylabel('CNR in dB')