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# rcsSignature

Radar cross-section pattern

## Description

rcsSignature creates a radar cross-section (RCS) signature object. You can use this object to model an angle-dependent and frequency-dependent radar cross-section pattern. The radar cross-section determines the intensity of reflected radar signal power from a target. The object models only non-polarized signals.

## Creation

### Description

rcssig = rcsSignature creates an rcsSignature object with default property values.

example

rcssig = rcsSignature(Name,Value) sets object properties using one or more Name,Value pair arguments. Name is a property name and Value is the corresponding value. Name must appear inside single quotes (''). You can specify several name-value pair arguments in any order as Name1,Value1,...,NameN,ValueN. Any unspecified properties take default values.

Note

You can only set property values of rcsSignature when constructing the object. The property values are not changeable after construction.

## Properties

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Sampled radar cross-section (RCS) pattern, specified as a scalar, a Q-by-P real-valued matrix, or a Q-by-P-by-K real-valued array. The pattern is an array of RCS values defined on a grid of elevation angles, azimuth angles, and frequencies. Azimuth and elevation are defined in the body frame of the target.

• Q is the number of RCS samples in elevation.

• P is the number of RCS samples in azimuth.

• K is the number of RCS samples in frequency.

Q, P, and K usually match the length of the vectors defined in the Elevation, Azimuth, and Frequency properties, respectively, with these exceptions:

• To model an RCS pattern for an elevation cut (constant azimuth), you can specify the RCS pattern as a Q-by-1 vector or a 1-by-Q-by-K matrix. Then, the elevation vector specified in the Elevation property must have length 2.

• To model an RCS pattern for an azimuth cut (constant elevation), you can specify the RCS pattern as a 1-by-P vector or a 1-by-P-by-K matrix. Then, the azimuth vector specified in the Azimuth property must have length 2.

• To model an RCS pattern for one frequency, you can specify the RCS pattern as a Q-by-P matrix. Then, the frequency vector specified in the Frequency property must have length 2.

Example: [10,0;0,-5]

Data Types: double

Azimuth angles used to define the angular coordinates of each column of the matrix or array, specified by the Pattern property. Specify the azimuth angles as a length-P vector. P must be greater than two. Angle units are in degrees.

Example: [-45:0.5:45]

Data Types: double

Elevation angles used to define the coordinates of each row of the matrix or array, specified by the Pattern property. Specify the elevation angles as a length-Q vector. Q must be greater than two. Angle units are in degrees.

Example: [-30:0.5:30]

Data Types: double

Frequencies used to define the applicable RCS for each page of the Pattern property, specified as a K-element vector of positive scalars. K is the number of RCS samples in frequency. K must be no less than two. Frequency units are in hertz.

Example: [0:0.1:30]

Data Types: double

## Object Functions

 value Radar cross-section at specified angle and frequency toStruct Convert to structure

## 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

Create an rcsSignature object and plot an elevation cut at $3{0}^{\circ }$ 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)')

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

## References

[1] Richards, Mark A. Fundamentals of Radar Signal Processing. New York, McGraw-Hill, 2005.

## See Also

### Classes

Introduced in R2018b

## Support

#### Sensor Fusion and Tracking for Autonomous Systems

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