# Backscatter Radar Target

Backscatter radar target

**Libraries:**

Phased Array System Toolbox /
Environment and Target

## Description

The Backscatter Radar Target block models the monostatic radar reflections of nonpolarized electromagnetic signals from a target. Target model includes all four Swerling target fluctuation models and non-fluctuating model. You can model several targets simultaneously by specifying multiple radar cross-section (RCS) matrices.

## Ports

### Input

**X** — Narrowband signal

*N*-by-*1* complex-valued
vector | *N*-by-*M* complex-valued
matrix

Narrowband nonpolarized signal, specified as an
*N*-by-*1* complex-valued vector
or an *N*-by-*M* complex-valued
matrix. The quantity *N* is the number of signal
samples and *M* is the number of signals reflecting
from the target. Each column corresponds to an independent signal
incident at a different reflecting angle.

The size of the first dimension of the input matrix can vary to simulate a changing signal length. A size change can occur, for example, in the case of a pulse waveform with variable pulse repetition frequency.

**Data Types: **`double`

**Ang** — Incident signal direction

2-by-1 real-valued column vector | 2-by-*M* real-valued column matrix

Incident signal direction, specified as a 2-by-1 real-valued column vector or a
2-by-*M* real-valued column matrix.
*M* is the number of signals reflecting from the
target. Each column of `Ang`

specifies the incident
direction of the corresponding signal in the form of an
`[AzimuthAngle;ElevationAngle]`

pair. Units are
degrees. The number of columns in `Ang`

must match
the number of independent signals in `X`

.

**Example: **`[30;45]`

**Data Types: **`double`

**Update** — Switch to update RCS

`false`

| `true`

Switch to update RCS fluctuation model values, specified as
`false`

or `true`

. When
`Update`

is `true`

, the RCS
value is updated. If `Update`

is
`false`

, the RCS remains unchanged.

#### Dependencies

To enable this port, set the **Fluctuation
model** drop-down menu to
`Swerling1`

,
`Swerling2`

,
`Swerling3`

, or
`Swerling4`

.

### Output

**Port_1** — Narrowband reflected signal

1-by-*M* complex-valued vector | *N*-by-*M* complex-valued
matrix

Narrowband nonpolarized signal, specified as an
1-by-*M* complex-valued vector or a
*N*-by-*M* complex-valued matrix.
Each column contains an independent signal reflected from the
target.

The quantity *N* is the number of signal samples and
*M* is the number of signals reflecting off the
target. Each column corresponds to a different reflecting angle.

The output port contains signal samples arriving at the signal destination within the current input time frame. When the propagation time from source to destination exceeds the current time frame duration, the output does not contain all contributions from the input of the current time frame.

## Parameters

**Azimuth angles (deg)** — Azimuth angles

`[-180:180]`

(default) | 1-by-*P* real-valued row vector | *P*-by-1 real-valued column vector

Specify the azimuth angles used to define the angular coordinates of the
**RCS pattern (m^2)** parameter. Specify azimuth angles
as a length *P* vector. Units are degrees.
*P* must be greater than two. This parameter determines
the incident azimuthal arrival angle of any element of the cross-section
patterns.

**Data Types: **`double`

**Elevation angles (deg)** — Elevation angles

`[-90:90]`

(default) | 1-by-*Q* real-valued row vector | *Q*-by-1 real-valued column vector

Specify the elevation angles used to define the angular coordinates of the
**RCS pattern (m^2)** parameter. Specify elevation
angles as a length *Q* vector. Units are degrees.
*Q* must be greater than two. This parameter determines
the incident elevation arrival angle of any element of the cross-section
patterns.

**RCS pattern (m^2)** — Radar cross-section pattern

`ones(181,361)`

(default) | *Q*-by-*P* real-valued matrix | *Q*-by-*P*-by-*M*
real-valued array | 1-by-*P* real-valued vector | *M*-by-*P* real-valued matrix

Radar cross-section pattern, specified as a
*Q*-by-*P* real-valued matrix or a
*Q*-by-*P*-by-*M*
real-valued array.

*Q*is the length of the vector in the**Elevation angles (deg)**parameter.*P*is the length of the vector in the**Azimuth angles (deg)**parameter.*M*is the number of target patterns. The number of patterns corresponds to the number of signals passed into the input port`X`

. You can, however, use a single pattern to model multiple signals reflecting from a single target.

You can, however, use a single pattern to model multiple signals reflecting from a single target. Pattern units are square-meters.

Pattern units are square-meters.

**Fluctuation model** — Target fluctuation model

`Nonfluctuating`

(default) | `Swerling1`

| `Swerling2`

| `Swerling3`

| `Swerling4`

Specify the statistical model of the target as either
`Nonfluctuating`

,
`Swerling1`

,
`Swerling2`

,
`Swerling3`

, or
`Swerling4`

. When you set this parameter to a
value other than `Nonfluctuating`

, you then set
radar cross-sections parameters using the `Update`

input
port.

**Propagation speed (m/s)** — Signal propagation speed

`physconst('LightSpeed')`

(default) | real-valued positive scalar

Signal propagation speed, specified as a real-valued positive scalar. The
default value of the speed of light is the value returned by
`physconst('LightSpeed')`

. Units are in meters per
second.

**Example: **`3e8`

**Data Types: **`double`

**Operating frequency (Hz)** — Operating frequency

`3e8`

(default) | positive scalar

Carrier frequency of the signal that reflects from the target, specified as a positive scalar. Units are in hertz.

**Data Types: **`double`

**Simulate using** — Block simulation method

`Interpreted Execution`

(default) | `Code Generation`

Block simulation, specified as `Interpreted Execution`

or
`Code Generation`

. If you want your block to use the
MATLAB^{®} interpreter, choose `Interpreted Execution`

. If
you want your block to run as compiled code, choose ```
Code
Generation
```

. Compiled code requires time to compile but usually runs
faster.

Interpreted execution is useful when you are developing and tuning a model. The block
runs the underlying System object™ in MATLAB. You can change and execute your model quickly. When you are satisfied
with your results, you can then run the block using ```
Code
Generation
```

. Long simulations run faster with generated code than in
interpreted execution. You can run repeated executions without recompiling, but if you
change any block parameters, then the block automatically recompiles before
execution.

This table shows how the **Simulate using** parameter affects the
overall simulation behavior.

When the Simulink^{®} model is in `Accelerator`

mode, the block mode specified
using **Simulate using** overrides the simulation mode.

**Acceleration Modes**

Block Simulation | Simulation Behavior | ||

`Normal` | `Accelerator` | `Rapid Accelerator` | |

`Interpreted Execution` | The block executes using the MATLAB interpreter. | The block executes using the MATLAB interpreter. | Creates a standalone executable from the model. |

`Code Generation` | The block is compiled. | All blocks in the model are compiled. |

For more information, see Choosing a Simulation Mode (Simulink).

#### Programmatic Use

Block
Parameter:`SimulateUsing` |

Type:enum |

Values:```
Interpreted
Execution
``` , `Code Generation` |

Default:```
Interpreted
Execution
``` |

## Version History

**Introduced in R2016a**

## See Also

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