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value

Radar cross-section at specified angle and frequency

Description

example

rcsval = value(rcssig,az,el,freq) returns the value, rcsval, of the radar cross-section (RCS) specified by the radar signature object, rcssig, computed at the specified azimuth az, elevation el, and frequency freq. If the specified azimuth and elevation is outside of the region in which the RCS signature is defined, the RCS value, rcsval, is returned as -Inf in dBsm.

[rcsval,expval] = value(rcssig,az,el,freq) returns the expected values of the radar cross-section.

Input Arguments

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Radar cross-section signature, specified as an rcsSignature object.

Azimuth angle, specified as scalar or length-M real-valued vector. Units are in degrees. The az, el, and freq arguments must have the same size. You can, however, specify one or two arguments as scalars, in which case the arguments are expanded to length-M.

Data Types: double

Elevation angle, specified as scalar or length-M real-valued vector. The az, el, and freq arguments must have the same size. You can, however, specify one or two arguments as scalars, in which case the arguments are expanded to length-M. Units are in degrees.

Data Types: double

RCS frequency, specified as a positive scalar or length-M vector with positive, real elements. The az, el, and freq arguments must have the same size. You can, however, specify one or two arguments as scalars, in which case the arguments are expanded to length-M vectors. Units are in Hertz.

Example: 100e6

Data Types: double

Output Arguments

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Radar cross-section, returned as a scalar or real-valued length-M vector. Units are in dBsm.

Expected values of radar cross section, returned as a scalar or as a real-valued length-M vector. The dimensions of expval are the same as rcsval. Units are in dBsm.

Data Types: double

Examples

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Specify the radar cross-section (RCS) of a triaxial ellipsoid and plot RCS values along an azimuth cut.

Specify the lengths of the axes of the ellipsoid. Units are in meters.

a = 0.15;
b = 0.20;
c = 0.95;

Create an RCS array. Specify the range of azimuth and elevation angles over which RCS is defined. Then, use an analytical model to compute the radar cross-section of the ellipsoid. Create an image of the RCS.

az = [-180:1:180];
el = [-90:1:90];
rcs = rcs_ellipsoid(a,b,c,az,el);
rcsdb = 10*log10(rcs);
imagesc(az,el,rcsdb)
title('Radar Cross-Section')
xlabel('Azimuth (deg)')
ylabel('Elevation (deg)')
colorbar

Figure contains an axes object. The axes object with title Radar Cross-Section contains an object of type image.

Create an rcsSignature object and plot an elevation cut at 30 azimuth.

rcssig = rcsSignature('Pattern',rcsdb,'Azimuth',az,'Elevation',el,'Frequency',[300e6 300e6]);
rcsdb1 = value(rcssig,30,el,300e6);
plot(el,rcsdb1)
grid
title('Elevation Profile of Radar Cross-Section')
xlabel('Elevation (deg)')
ylabel('RCS (dBsm)')

Figure contains an axes object. The axes object with title Elevation Profile of Radar Cross-Section contains an object of type line.

function rcs = rcs_ellipsoid(a,b,c,az,el)
sinaz = sind(az);
cosaz = cosd(az);
sintheta = sind(90 - el);
costheta = cosd(90 - el);
denom = (a^2*(sintheta'.^2)*cosaz.^2 + b^2*(sintheta'.^2)*sinaz.^2 + c^2*(costheta'.^2)*ones(size(cosaz))).^2;
rcs = (pi*a^2*b^2*c^2)./denom;
end

Algorithms

The RCS signature, is first linearly interpolated at the specified azimuth, az, and elevation, el, view angles for the provided frequencies, freq. The interpolated signature is then used as an expected value of a probability distribution that generates a signature pattern value according to the RCS fluctuation model specified by the FluctuationModel property.. az and el are specified in degrees and are defined in the body frame of the pattern. freq is in hertz.

If FluctuationModel is 'Swerling0', the returned pattern value is a deterministic constant equal to the interpolated signature.

If FluctuationModel is 'Swerling1', the returned pattern value is a random variable distributed according to an exponential distribution with a mean value equal to the interpolated signature.

If FluctuationModel is 'Swerling3', the returned pattern value is a random variable distributed according to a chi-square distribution with four degrees of freedom and a mean value equal to the interpolated signature.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Version History

Introduced in R2018b

See Also

(Radar Toolbox) | |