surfaceReflectivity

Obtain the constant gamma normalized reflectivity for using the default gamma value of -20 dB at a frequency of 10 GHz and a grazing angle of 10 degrees.

grazAng = 10;
freq = 10e9;
refl = surfaceReflectivity

refl = 
  surfaceReflectivityLand with properties:

    EnablePolarization: 0
                 Model: 'ConstantGamma'
                 Gamma: -20
               Speckle: 'None'

nrcs = refl(grazAng,freq)

nrcs = 0.0017

Create a normalized reflectivity cross-section object for a land surface using the GIT model and a soil land type. Obtain the NRCS at a frequency of 10 GHz over grazing angles from 20 to 60 degrees. Assume a standard deviation of surface height of 1 m.

grazAng = 20:60;
freq    = 10e9;
refl = surfaceReflectivity('Land','Model','GIT','LandType','Soil', ...
    'SurfaceHeightStandardDeviation',1);
nrcs = refl(grazAng,freq);

Plot normalized reflectivities for grazing angles from 20 to 60 degrees.

plot(grazAng,pow2db(nrcs))
grid on
xlabel('Grazing Angle (deg)')
ylabel('NRCS (dB m^2/m^2)')
title('GIT Model')

Create a sea normalized reflectivity object using the default NRL model and a sea state of 2. Obtain the normalized reflectivity at 10 GHz over grazing angles from 0.1 to 10 degrees. Assume horizontal polarization.

grazAng = 0.1:0.1:10;
freq = 10e9;
ss = 2;
pol = 'H';

Use the surfaceReflectivity object to obtain the normalized reflectivity.

refl = surfaceReflectivity('Sea',SeaState = ss,Polarization = pol);
nrcs = refl(grazAng,freq);

Plot the reflectivity as a function of grazing angle.

plot(grazAng,pow2db(nrcs))
grid on
xlabel('Grazing Angle (deg)')
ylabel('NRCS (dB m^2/m^2)')
title('NRL Model, Horizontal Polarization')

Define a custom NRCS table using Nathanson reflectivity values for farmlands. Assume Rayleigh speckle. Next, calculate the RCS of a clutter patch and estimate the clutter-to-noise ratio at the receiver. Assume that the patch is 1000 meters away from the radar system. The azimuth and elevation beamwidths are 1 degree and 3 degrees, respectively. The grazing angle is 10 degrees. The pulse width is 10 microseconds. The radar operates at an L-band frequency of 1.5 GHz with a peak power of 5 kw. Use the general surfaceReflectivity object.

rng    = 1000;
bwAz   = 1;
bwEl   = 3;
graz   = 10;
tau    = 10e-6;
freq   = 1.5e9;
ppow   = 5000;

Configure a custom surface.

nathansonNRCS = db2pow([-35 -33 -32; -31 -30 -29; -29 -27 -25; ...
    -19 -17 -15; -14 -15 -14]);
nathansonFreq    = [1.5 3 6]*1e9;
nathansonGrazAng = [1.5 3 10 30 60];
refl = surfaceReflectivity('Custom',Reflectivity = nathansonNRCS, ...
    Frequency = nathansonFreq,GrazingAngle = nathansonGrazAng, ...
    Speckle = "Rayleigh")

refl = 
  surfaceReflectivityCustom with properties:

    EnablePolarization: 0
          Reflectivity: [5x3 double]
             Frequency: [1.5000e+09 3.0000e+09 6.0000e+09]
          GrazingAngle: [1.5000 3 10 30 60]
               Speckle: 'Rayleigh'
          SpeckleScale: 0.7979

[nrcs,n] = refl(graz,freq)

nrcs = 0.0013

n = 0.5108

Calculate the clutter RCS and apply multiplicative speckle

sigma = clutterSurfaceRCS(nrcs,rng,bwAz,bwEl,graz,tau)

sigma = 6.6253

rcs = sigma.*n   

rcs = 3.3841

Calculate clutter-to-noise ratio.

lambda = freq2wavelen(freq);
cnr = radareqsnr(lambda,rng,ppow,tau,'rcs',rcs)

cnr = 69.2976