irSignature

Infrared platform signature

Description

The irSignature creates an infrared (IR) signature object. You can use this object to model an angle-dependent contrast radiant intensity of a platform. The radiant intensity is with respect to the background.

Creation

Syntax

irsig = irSignature

irsig = irSignature(Name,Value)

Description

irsig = irSignature creates an irSignature object with default property values.

irsig = irSignature(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 irSignature when constructing the object. The property values are not changeable after construction.

Properties

Pattern — Sampled IR intensity pattern

[50 50; 50 50] (default) | Q-by-P real-valued matrix

Sampled contrast IR intensity pattern, specified as a scalar, or a Q-by-P real-valued matrix. The pattern is an array of IR values defined on a grid of elevation angles and azimuth angles. Azimuth and elevation are defined in the body frame of the target. Units are dBw/sr.

• Q is the number of IR samples in elevation.

• P is the number of IR samples in azimuth.

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

• If you want to model an IR pattern for an elevation cut (constant azimuth), you can specify the IR pattern as a Q-by-1 vector. Then, the elevation vector specified in the Elevation property must have length-2.

• If you want to model an IR pattern for an azimuth cut (constant elevation), you can specify the IR pattern as a 1-by-P vector. Then, the azimuth vector specified in the Azimuth property must have length-2.

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

Data Types: double

Azimuth — Azimuth angles

[-180 180] (default) | length-P real-valued vector

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 — Elevation angles

[-90 90] (default) | length-Q real-valued vector

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

Frequency — Pattern frequencies

[0 1e20] (default) | K-element vector of positive scalars

Frequencies used to define the applicable IR intensity 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	Infrared intensity at specified angle and frequency
toStruct	Convert to structure

Examples

Create Direction-Dependent IR Signature

Create and display an IR intensity signature. The signature depends on azimuth and elevation.

Define the azimuth and elevation angle sample points.

az = -90:90;
el = [-30:30];

Create the IR intensity signature pattern.

pat = 50*cosd(2*el.')*cosd(az).^2;
irsig = irSignature('Pattern',pat,'Azimuth',az,'Elevation',el);

Display the IR pattern.

imagesc(irsig.Azimuth,irsig.Elevation,irsig.Pattern)
xlabel('Azimuth (deg)')
ylabel('Elevation')
title('Infrared Signature Pattern (dBw/sr)')

Get the IR intensity value at 25 degrees azimuth and 10 degrees elevation.

value(irsig,25,10)

ans = 
38.5929

Get IR intensity value outside of the valid elevation span.

value(irsig,25,35)

ans = 
-Inf

Extended Capabilities

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

Version History

Introduced in R2018b