MATLAB Examples

# Figure 7. Clutter Loci for Different Platform Velocities.

## Contents

clc; clear; close all; 

radar_oper_params; % Azimuth angle in degrees: phi = -180:.5:180; Lphi = length(phi); 

## Platform Parameters.

va = 50; % Platform velocity in m/sec. ha = 9e3; % Platform altitude in meters. beta = 0:0.5:7; % Beta parameter values. Rc = 13e4; % (clutter) range of interest in meters. psi = asin(ha/Rc); % Grazing angle at the clutter patch in rad (flat earth model). theta = psi; % Depression angle to ik-th clutter patch (flat earth model). 

## Spatial Frequency of ik-th Clutter Patch

fsp = d/lambda*cos(theta)*sin(phi*pi/180); 

## Calculate and Plot the Clutter Loci for Different Platform Velocities

figure('NumberTitle', 'off','Name', ... 'Figure 7. Clutter Loci for Different Velocities of Side Looking Airborne Radar (SLAR) ', ... 'Position', [50 50 1150 700] ); for i=1:length(beta) % Platform Velocity for various beta parameter values: va = beta(i)*d*fr/2; % Eq. (71) % Doppler Frequency from ik-th Clutter Patch % fd = 2*va/lambda*cos(theta)*sin(phi*pi/180); % Normalized Doppler Frequency: % omegac = 2*va*Tr/d*fsp; omegac = beta(i)*fsp; % Eq. (70) % This loop simulates the fold-over of the Clutter ridge (i.e. brings omegac % back into the [-0.5 0.5] interval) when clutter is Doppler-ambiguous (β>1). for k=1:Lphi if omegac(k)>0.5 && omegac(k)<=1.5 omegac(k) = omegac(k) - 1; elseif omegac(k)<-0.5 && omegac(k)>=-1.5 omegac(k) = omegac(k) + 1; end if omegac(k)>1.5 && omegac(k)<=2.5 omegac(k) = omegac(k) - 2; elseif omegac(k)<-1.5 && omegac(k)>=-2.5 omegac(k) = omegac(k) + 2; end if omegac(k)>2.5 && omegac(k)<=3.5 omegac(k) = omegac(k) - 3; elseif omegac(k)<-2.5 && omegac(k)>=-3.5 omegac(k) = omegac(k) + 3; end end % Plot Normalized Doppler Frequency vs Spatial Frequency. subplot(3,5,i); plot(fsp,omegac,'.'); title(['v_a = ',num2str(round(va)),' m/sec, \bf\beta = ',num2str(beta(i))]); if i==1 || i== 6 || i==11 ylabel('Norm. Doppler Frequency \omega_c'); end if i>10 xlabel('Spatial Frequency \vartheta_c'); end ylim([-0.5 0.5]); xlim([-0.5 0.5]); grid on; end tightfig;