## 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 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, specify the `EnablePolarization` property as `false`. To utilize polarization, 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, specify the radar cross-section as a 2-by-2 scattering matrix in the `ScatteringMatrix` property. For both polarization processing types, there are several Swerling models available that can generate random fluctuations in the RCS. Choose these models using the `Model` property. The `SeedSource` and `Seed` properties control the random fluctuations.

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

EnablePolarization ValueUse These Properties
`false`
• `MeanRCSSource`

• `MeanRCS`

`true`
• `ScatteringMatrixSource`

• `ScatteringMatrix`

• `Mode`

To compute the signal reflected from a radar target:

1. Define and set up your radar target. See Construction.

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 reflected signal direction is opposite to its incoming direction. If you set this property to `'Bistatic'`, the reflected direction of the signal differs from its incoming direction. This property applies when you set the `EnablePolarization` property to `true`.

Default: `'Monostatic'`

`ScatteringMatrixSource`

Sources of mean scattering matrix of target

Source of mean scattering matrix of target 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 for polarized signal

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. Units are 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 1i]`

`MeanRCSSource`

Source of mean radar cross section

Specify whether the mean RCS value of the target 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 the `ScatteringMatrix` property.

Default: `'Property'`

`MeanRCS`

Mean radar cross section

Specify the mean value of the target's radar cross section as a nonnegative scalar or as a 1-by-M real-valued, nonnegative row vector. Units are in square meters. Using a vector lets you simultaneously process multiple targets. The quantity M is 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 value.

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
`release`

Allow System object property value changes

## Examples

collapse all

Create a simple signal and compute the value of the reflected signal from a target having a radar cross section of $10{m}^{2}$. Set the radar cross section using the `MeanRCS` property. Set the radar operating frequency to 600 MHz.

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

This value agrees with the formula $y=\sqrt{G}x$ where

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

## 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.