# Range Response

Range response

**Libraries:**

Phased Array System Toolbox /
Detection

## Description

The Range Response block performs range filtering on fast-time (range) data, using either a matched filter or an FFT-based algorithm. The output is typically used as input to a detector. Matched filtering improves the SNR of pulsed waveforms. For continuous FM signals, FFT processing extracts the beat frequency of FMCW waveforms. Beat frequency is directly related to range.

The input to the block is a radar data cube. The organization of the data cube follows the Phased Array System Toolbox™ convention. The first dimension of the cube represents the fast time samples or ranges of the received signals. The second dimension represents multiple spatial channels such as different sensors or beams. The third dimension, slow time, represent pulses. Range filtering operates along the fast-time dimension of the cube. Processing along the other dimensions is not performed. If the data contains only one channel or pulse, the data cube can contain fewer than three dimensions. Because this object performs no Doppler processing, you can use it to process noncoherent radar pulses.

The output of the block is also a data cube with the same number of dimensions as the input. Its first dimension contains range-processed data but its length can differ from the first dimension of the input data cube.

## Ports

### Input

**X** — Input data cube

complex-valued *K*-by-1 column vector | complex-valued *K*-by-*L* matrix | complex-valued *K*-by-*N*-by-*L* array

Input data cube, specified as a complex-valued *K*-by-1
column vector, a complex-valued *K*-by-*L* matrix,
or a complex-valued *K*-by-*N*-by-*L* array.

*K*is the number of range or time samples.*N*is the number of independent channels such as sensors or directions.*L*is the number of pulses or sweeps in the input signal.

Each *K*-element column vector is processed
independently.

For an FMCW waveform, with a triangle sweep, the sweeps alternate between positive and negative slopes. However, Range Response is designed to process consecutive sweeps of the same slope. To apply the Range Response block for a triangle-sweep system, use one of the following approaches:

Specify a positive

**Sweep slope**parameter value, with`X`

corresponding to upsweeps only. After obtaining the Doppler or speed values, divide them by 2.Specify a negative

**Sweep slope**parameter value, with`X`

corresponding to downsweeps only. After obtaining the Doppler or speed values, divide them by 2.

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`

**Complex Number Support: **Yes

**Coeff** — Matched filter coefficients

complex-valued column vector

Matched filter coefficients, specified as a complex-valued column
vector. The length of the vector must be less than or equal to the
number of rows in the input data, *K*.

#### Dependencies

To enable this port, set **Range processing method** to ```
Matched
filter
```

.

**Data Types: **`double`

**Complex Number Support: **Yes

**XRef** — Reference signal

complex-valued *K*-by-1 column vector

Reference signal used for dechirping the input signal, specified
as a complex-valued *K*-by-1 column vector. The
number of rows must equal the length of the first dimension of `X`

.

#### Dependencies

To enable this port, set **Range processing method** to `FFT`

and
select the **Dechirp input signal** parameter.

**Data Types: **`double`

**Complex Number Support: **Yes

### Output

**Resp** — Range response data cube

complex-valued *M*-element column vector | complex-valued *M*-by-*L* matrix | complex-valued *M*-by-*N* by-*L* array

Range response data cube, returned as a

Complex-valued

*M*-element column vectorComplex-valued

*M*-by-*L*matrixComplex-valued

*M*-by-*N*by-*L*array

See Radar Data Cube Concept. The value of *M* depends
on the type of processing

Range processing method | Dechirp input signal | Value
of M |
---|---|---|

`FFT` | `off` | If you set the |

`on` | M equals the number of rows, K,
of the input signal. | |

`Matched filter` | N/A | M equals the number of rows, K,
of the input signal. |

**Data Types: **`double`

**Complex Number Support: **Yes

**Range** — Range values along range dimension

real-valued *M*-by-1 column vector

Range values along the first dimension of the **Resp** output
data port, specified as a real-valued *M*-by-1 column
vector. This quantity defines the range values along the first dimension
of the `Resp`

output port data. Units are in meters.

**Data Types: **`double`

## Parameters

**Range processing method** — Range processing method

`Matched filter`

(default) | `FFT`

Range processing method, specified as `Matched filter`

or `FFT`

.

`Matched filter` | The block applies a matched filter to the incoming signal. This approach is commonly used for pulsed signals, where the matched filter is the time reverse of the transmitted signal. |

`FFT` | The block applies an FFT to the input signal. This approach is commonly used for FMCW and linear FM pulsed signals. |

**Data Types: **`char`

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

`physconst('LightSpeed')`

(default) | 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')`

.

**Data Types: **`double`

**Inherit sample rate** — Inherit sample rate from upstream blocks

on (default) | off

Select this parameter to inherit the sample rate from upstream blocks. Otherwise,
specify the sample rate using the **Sample rate (Hz)**
parameter.

**Data Types: **`Boolean`

**Sample rate (Hz)** — Sampling rate of signal

`1e6`

(default) | positive real-valued scalar

Specify the signal sampling rate as a positive scalar. Units are in Hz.

#### Dependencies

To enable this parameter, clear the **Inherit sample rate** check
box.

**Data Types: **`double`

**FM sweep slope (Hz/s)** — FM sweep slope

`1e9`

(default) | scalar

Specify the slope of the linear FM sweep as a scalar. This parameter
must match the actual sweep of the input data in port `X`

.

#### Dependencies

To enable this parameter, set **Range processing method** to `FFT`

.

**Data Types: **`double`

**Dechirp input signal** — Enable dechirping of input signal

`on`

(default) | `off`

Select this parameter to enable dechirping of input signal.

#### Dependencies

To enable this parameter, set **Range processing method** to `FFT`

.

**Data Types: **`Boolean`

**Source of FFT length in range processing** — Source of FFT length for range processing

`Auto`

(default) | `Property`

Source of FFT length for range processing, specified as `Auto`

or `Property`

`Auto` | The FFT length equals the number of rows of the input data cube. |

`Property` | Specify FFT length in the FFT length in range processing parameter. |

#### Dependencies

To enable this parameter, set **Range processing method** to
`FFT`

.

**Data Types: **`char`

**FFT length in range processing** — Range processing FFT length

`1024`

(default) | positive integer

FFT length for range processing, specified as a positive integer.

#### Dependencies

To enable this parameter, set **Range processing method** to `FFT`

and **Source
of FFT length in range processing** to `Property`

.

**Data Types: **`double`

**Range processing window** — Range FFT weighting window

`None`

(default) | `Hamming`

| `Chebyshev`

| `Hann`

| `Kaiser`

| `Taylor`

Range FFT weighting window, specified as `None`

, `Hamming`

, `Chebyshev`

, `Hann`

, `Kaiser`

,
or `Taylor`

.

If you set this property to `Taylor`

, the generated
Taylor window has four nearly constant sidelobes next to the mainlobe.

#### Dependencies

To enable this parameter, set **Range processing method** to `FFT`

.

**Data Types: **`char`

**Range sidelobe attenuation level** — Sidelobe attenuation for range processing

`30`

(default) | positive scalar

Sidelobe attenuation for range processing, specified as a positive scalar. Units are in dB.

#### Dependencies

To enable this parameter, set **Range processing method** to `FFT`

and **Range
processing window** to `Kaiser`

, `Chebyshev`

,
or `Taylor`

.

**Data Types: **`double`

**Set reference range at center** — Set reference range at center of range grid

`on`

(default) | `off`

Set reference range at the center of range grid, specified as
`on`

or `off`

. Selecting this check
box, enables you to set the reference range at the center of the range grid.
Otherwise, the reference range is set to the beginning of the range
grid.

#### Dependencies

To enable this property, set the **Range processing
method** to `FFT`

.

**Reference range (m)** — Reference range of range grid

`0.0`

(default) | nonnegative scalar

Reference range of the range grid, specified as a nonnegative scalar.

If you set the

**Range processing method**parameter to`Matched filter`

, the reference range is set to the start of the range grid.If you set the

**Range processing method**property to`FFT`

, the reference range depends on the**Set reference range at center**check box.When you select the

**Set reference range at center**check box, the reference range is set to the center of the range grid.If you do not select the

**Set reference range at center**check box, the reference range is set to the start of the range grid.

Units are in meters.

**Example: **`1000.0`

**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
``` |

## References

[1] Richards, M. *Fundamentals of Radar Signal
Processing, 2nd ed*. McGraw-Hill Professional Engineering,
2014.

[2] Richards, M., J. Scheer, and W. Holm, * Principles
of Modern Radar: Basic Principles*. SciTech Publishing,
2010.

## Version History

**Introduced in R2017a**

## See Also

### Blocks

### Functions

### Objects

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