# rcscylinder

Radar cross section of cylinder

## Description

example

rcspat = rcscylinder(r1,r2,height,c,fc) returns the radar cross section pattern of an elliptical cylinder having a semi-major axis, r1, a semi-minor axis, r2, and a height, height. The radar cross section is a function of signal frequency, fc, and signal propagation speed,c. The bottom of the cylinder lies on the xy-plane. The height of the cylinder points along the positive z-axis.

example

rcspat = rcscylinder(r1,r2,height,c,fc,az,el) also specifies the azimuth angles, az, and elevation angles, el, at which to compute the radar cross section.

example

[rcspat,azout,elout] = rcscylinder(___) also returns the azimuth angles, azout, and elevation angles, elout, at which the radar cross sections are computed. You can use these output arguments with any of the previous syntaxes.

## Examples

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Display the radar cross section (RCS) pattern as a function of azimuth and elevation for an elliptical cylinder whose semi-major axis is 12.5 cm and whose semi-minor axis is 9 cm. The cylinder height is 1 m. The operating frequency is 4.5 GHz.

Specify the cylinder geometry and signal parameters.

c = physconst('Lightspeed');
fc = 4.5e9;
hgt = 1;

Compute the RCS for all directions using the default direction values.

imagesc(azresp,elresp,pow2db(rcspat))
colorbar
xlabel('Azimuth Angle (deg)')
ylabel('Elevation Angle (deg)')
title('Elliptic Cylinder RCS (dBsm)')

Plot the radar cross section (RCS) pattern of an elliptical cylinder as a function of elevation at a constant azimuth angle of 5${}^{\circ }$. The cylinder has a semi-major axis of 12.5 cm and a semi-minor axis of 9 cm. The cylinder height is 1 m. The operating frequency is 4.5 GHz.

Specify the cylinder geometry and signal parameters.

c = physconst('Lightspeed');
fc = 4.5e9;
hgt = 1;

Compute the RCS for all elevation angles at a fixed azimuth angle of 5${}^{\circ }$.

el = -90:90;
az = 5;
plot(elresp,pow2db(rcspat))
xlabel('Elevation Angle (deg)')
ylabel('RCS (dBsm)')
title('Elliptic Cylinder RCS as Function of Elevation')
grid on

Plot the radar cross section (RCS) of an elliptical cylinder as a function of frequency for a fixed direction. The cylinder has as semi-major axis of 12.5 cm and a semi-minor axis of 9 cm. The cylinder height is 1 m.

Specify the cylinder geometry and signal parameters.

c = physconst('Lightspeed');
hgt = 1;

Compute radar cross sections as a function of frequency for a fixed azimuth and elevation.

az = 5.0;
el = 20.0;
fc = (100:100:4000)*1e6;
disp([azpat,elpat])
5    20
plot(fc/1e6,pow2db(squeeze(rcspat)))
xlabel('Frequency (MHz)')
ylabel('RCS (dBsm)')
title('Cylinder RCS as Function of Frequency')
grid on

## Input Arguments

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Length of semi-major axis of cylinder, specified as a positive scalar. Units are in meters.

Example: 5.5

Data Types: double

Length of semi-minor axis of cylinder, specified as a positive scalar. Units are in meters.

Example: 3.0

Data Types: double

Height of cylinder, specified as a positive scalar. Units are in meters.

Example: 3.0

Data Types: double

Signal propagation speed, specified as a positive scalar. Units are in meters per second. For the SI value of the speed of light, use physconst('LightSpeed').

Example: 3e8

Data Types: double

Frequency for computing radar cross section, specified as a positive scalar or positive, real-valued, 1-by-L row vector. Frequency units are in Hz.

Example: [100e6 200e6]

Data Types: double

Azimuth angles for computing directivity and pattern, specified as a real-valued 1-by-M row vector where M is the number of azimuth angles. Angle units are in degrees. Azimuth angles must lie between –180° and 180°, inclusive.

The azimuth angle is the angle between the x-axis and the projection of a direction vector onto the xy-plane. The azimuth angle is positive when measured from the x-axis toward the y-axis.

Example: -45:2:45

Data Types: double

Elevation angles for computing directivity and pattern, specified as a real-valued, 1-by-N row vector where N is the number of desired elevation directions. Angle units are in degrees. Elevation angles must lie between –90° and 90°, inclusive.

The elevation angle is the angle between a direction vector and xy-plane. The elevation angle is positive when measured towards the z-axis.

Example: -75:1:70

Data Types: double

Tip

To construct a circular cylinder, set r2 equal to r1.

## Output Arguments

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Radar cross section pattern, returned as a real-valued N-by-M-by-L array. N is the length of the vector returned in the elout argument. M is the length of the vector returned in the azout argument. L is the length of the fc vector. Units are in meters-squared.

Data Types: double

Azimuth angles for computing directivity and pattern, returned as a real-valued 1-by-M row vector where M is the number of azimuth angles specified by the az input argument. Angle units are in degrees.

The azimuth angle is the angle between the x-axis and the projection of the direction vector onto the xy-plane. The azimuth angle is positive when measured from the x-axis toward the y-axis.

Data Types: double

Elevation angles for computing directivity and pattern, returned as a real-valued 1-by-N row vector where N is the number of elevation angles specified in el output argument. Angle units are in degrees.

The elevation angle is the angle between the direction vector and xy-plane. The elevation angle is positive when measured towards the z-axis.

Data Types: double

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### Azimuth and Elevation

This section describes the convention used to define azimuth and elevation angles.

The azimuth angle of a vector is the angle between the x-axis and its orthogonal projection onto the xy-plane. The angle is positive when going from the x-axis toward the y-axis. Azimuth angles lie between –180° and 180° degrees, inclusive. The elevation angle is the angle between the vector and its orthogonal projection onto the xy-plane. The angle is positive when going toward the positive z-axis from the xy-plane. Elevation angles lie between –90° and 90° degrees, inclusive.

## References

[1] Mahafza, Bassem. Radar Systems Analysis and Design Using MATLAB, 2nd Ed. Boca Raton, FL: Chapman & Hall/CRC, 2005.