# Documentation

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## Description

The `RadarTarget` System object™ models how a signal is reflected from a radar target. The quantity that determines the response of a target to an incoming signals is called the radar target cross-section (RCS). While all electromagnetic radar signals are polarized, you can sometimes ignore polarization and process them as if they were scalar signals. To ignore polarization, you should specify the `EnablePolarization` property as `false`. To utilize polarization, you must specify the `EnablePolarization` property as `true`. For non-polarized processing, the radar cross section is encapsulated in a single scalar quantity called the `MeanRCS`. For polarized processing, the radar cross-section is more generally expressed by a 2-by-2 scattering matrix in the `ScatteringMatrix` property. For both polarization processing types, there are several Swerling models available to be used to generate random fluctuations in the RCS. These models are chosen using the `Model` property. The random fluctuations are controlled by the `SeedSource` and `Seed` properties.

The properties that you can use to model the radar cross-section or scattering matrix depend upon the polarization type.

`EnablePolarization`Use these properties
`false`
• `MeanRCSSource`

• `MeanRCS`

`true`
• `ScatteringMatrixSource`

• `ScatteringMatrix`

• `Mode`

To compute the signal reflected from a radar target:

2. Call `step` to compute the reflected signal according to the properties of `phased.RadarTarget`. The behavior of `step` is specific to each object in the toolbox.

### Note

Starting in R2016b, instead of using the `step` method to perform the operation defined by the System object, you can call the object with arguments, as if it were a function. For example, ```y = step(obj,x)``` and `y = obj(x)` perform equivalent operations.

## Construction

`H = phased.RadarTarget` creates a radar target System object, `H`, that computes the reflected signal from a target.

`H = phased.RadarTarget(Name,Value)` creates a radar target object, `H`, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (`Name1`,`Value1`,...,`NameN`,`ValueN`).

## Properties

`EnablePolarization`

Allow polarized signals

Set this property to `true` to allow the target to simulate the reflection of polarized radiation. Set this property to `false` to ignore polarization.

Default: `false`

`Mode`

Target scattering mode

Target scattering mode specified as one of `'Monostatic'` or `'Bistatic'`. If you set this property to `'Monostatic'`, the signal's reflection direction is the opposite to its incoming direction. If you set this property to `'Bistatic'`, the signal's reflection direction differs from its incoming direction. This property applies when you set the `EnablePolarization` property to `true`.

Default: `'Monostatic'`

`ScatteringMatrixSource`

Source of target mean scattering matrix

Source of target mean scattering matrix specified as one of `'Property'` or ```'Input port'```. If you set the `ScatteringMatrixSource` property to `'Property'`, the target’s mean scattering matrix is determined by the value of the `ScatteringMatrix` property. If you set this property to `'Input port'`, the mean scattering matrix is determined by an input argument of the `step` method. This property applies only when you set the `EnablePolarization` property to `true`. When the `EnablePolarization` property is set to `false`, use the `MeanRCSSource` property instead, together with the `MeanRCS` property, if needed.

Default: `'Property'`

`ScatteringMatrix`

Mean radar scattering matrix specified as a complex–valued 2-by-2 matrix. This matrix represents the mean value of the target's radar cross-section (in square meters). The matrix has the form ```[s_hh s_hv;s_vh s_vv]```. In this matrix, the component `s_hv` specifies the complex scattering response when the input signal is vertically polarized and the reflected signal is horizontally polarized. The other components are defined similarly. This property applies when you set the `ScatteringMatrixSource` property to `'Property'` and the `EnablePolarization` property to `true`. When the `EnablePolarization` property is set to `false`, use the `MeanRCS` property instead, together with the `MeanRCSSource` property. This property is tunable.

Default: `[1 0;0 1]`

`MeanRCSSource`

Source of mean radar cross section

Specify whether the target’s mean RCS value(s) comes from the `MeanRCS` property of this object or from an input argument in `step`. Values of this property are:

 `'Property'` The `MeanRCS` property of this object specifies the mean RCS value(s). `'Input port'` An input argument in each invocation of `step` specifies the mean RCS value.

When `EnablePolarization` property is set to `true`, use the `ScatteringMatrixSource` property together with `ScatteringMatrix`.

Default: `'Property'`

`MeanRCS`

Specify the mean value of the target's radar cross section (in square meters) as a nonnegative scalar or as a 1-by-M nonnegative row vector. Using a vector allows you to process multiple targets simultaneous. The quantity Mis the number of targets. This property is used when `MeanRCSSource` is set to `'Property'`. This property is tunable.

When `EnablePolarization` property is set to `true`, use the `ScatteringMatrix` property together with the `ScatteringMatrixSource`.

Default: `1`

`Model`

Target statistical model

Specify the statistical model of the target as one of `'Nonfluctuating'`, `'Swerling1'`, `'Swerling2'`, `'Swerling3'`, or `'Swerling4'`. If you set this property to a value other than `'Nonfluctuating'`, you must use the `UPDATERCS` input argument when invoking `step`. You can set the mean value of the radar cross-section model by specifying `MeanRCS` or use its default va;ue.

Default: `'Nonfluctuating'`

`PropagationSpeed`

Signal propagation speed

Specify the propagation speed of the signal, in meters per second, as a positive scalar.

Default: Speed of light

`OperatingFrequency`

Signal carrier frequency

Specify the carrier frequency of the signal you are reflecting from the target, as a scalar in hertz.

Default: `3e8`

`SeedSource`

Source of seed for random number generator

Specify how the object generates random numbers. Values of this property are:

 `'Auto'` The default MATLAB® random number generator produces the random numbers. Use `'Auto'` if you are using this object with Parallel Computing Toolbox™ software. `'Property'` The object uses its own private random number generator to produce random numbers. The `Seed` property of this object specifies the seed of the random number generator. Use `'Property'` if you want repeatable results and are not using this object with Parallel Computing Toolbox software.

The random numbers are used to model random RCS values. This property applies when the `Model` property is `'Swerling1'`, `'Swerling2'`,`'Swerling3'`, or `'Swerling4'`.

Default: `'Auto'`

`Seed`

Seed for random number generator

Specify the seed for the random number generator as a scalar integer between 0 and 232–1. This property applies when you set the `SeedSource` property to `'Property'`.

Default: `0`

## Methods

 reset Reset states of radar target object step Reflect incoming signal
Common to All System Objects
`clone`

Create System object with same property values

`getNumInputs`

Expected number of inputs to a System object

`getNumOutputs`

Expected number of outputs of a System object

`isLocked`

Check locked states of a System object (logical)

`release`

Allow System object property value changes

## Examples

expand all

Create a simple signal and compute the value of the reflected signal from a target having a radar cross section of . Set the radar cross section using the `MeanRCS` property. Set the radar operating frequency to 600 MHz.

```x = ones(10,1); sRadarTarget = phased.RadarTarget('Model','Nonfluctuating',... 'MeanRCS',10,... 'OperatingFrequency',600e6); y = step(sRadarTarget,x); disp(y(1:3))```
``` 22.4355 22.4355 22.4355 ```

This value agrees with the formula where

## Algorithms

For a narrowband nonpolarized signal, the reflected signal, Y, is

`$Y=\sqrt{G}\cdot X,$`

where:

• X is the incoming signal.

• G is the target gain factor, a dimensionless quantity given by

`$G=\frac{4\pi \sigma }{{\lambda }^{2}}.$`

• σ is the mean radar cross-section (RCS) of the target.

• λ is the wavelength of the incoming signal.

The incident signal on the target is scaled by the square root of the gain factor.

For narrowband polarized waves, the single scalar signal, X, is replaced by a vector signal, (EH, EV), with horizontal and vertical components. The scattering matrix, S, replaces the scalar cross-section, σ. Through the scattering matrix, the incident horizontal and vertical polarized signals are converted into the reflected horizontal and vertical polarized signals.

`$\left[\begin{array}{c}{E}_{H}^{\left(scat\right)}\\ {E}_{V}^{\left(scat\right)}\end{array}\right]=\sqrt{\frac{4\pi }{{\lambda }^{2}}}\left[\begin{array}{cc}{S}_{HH}& {S}_{VH}\\ {S}_{HV}& {S}_{VV}\end{array}\right]\left[\begin{array}{c}{E}_{H}^{\left(inc\right)}\\ {E}_{V}^{\left(inc\right)}\end{array}\right]=\sqrt{\frac{4\pi }{{\lambda }^{2}}}\left[S\right]\left[\begin{array}{c}{E}_{H}^{\left(inc\right)}\\ {E}_{V}^{\left(inc\right)}\end{array}\right]$`

For further details, see Mott, [1] or Richards, [2] .

## References

[1] Mott, H., Antennas for Radar and Communications, John Wiley & Sons, 1992.

[2] Richards, M. A. Fundamentals of Radar Signal Processing. New York: McGraw-Hill, 2005.

[3] Skolnik, M. Introduction to Radar Systems, 3rd Ed. New York: McGraw-Hill, 2001.