Stretch Processor

Stretch processor for linear FM waveforms

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Libraries:
Phased Array System Toolbox / Detection

Description

The Stretch Processor block applies stretch processing on a linear FM waveform. Also known as dechirping, stretch processing is an alternative to matched filtering for linear FM waveforms.

Ports

Input

X — Input signal

M-by-P complex-valued matrix

Input signal, specified as an M-by-P complex-valued array. M is the number of samples and P is the number of pulses.

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

PRF — Pulse repetition frequency

positive scalar

Pulse repetition frequency of current pulse, specified as a positive scalar.

Dependencies

To enable this port, set the Specify PRF as parameter to Input port.

Data Types: double

Output

Y — Stretch processed signal

M-by-P complex-valued matrix

Stretch processed signal, returned as an M-by-P complex-valued array. M is the number of samples and P is the number of pulses.

Data Types: double
Complex Number Support: Yes

Parameters

Pulse width (s) — Time duration of pulse

50e-6 (default) | positive scalar

The duration of each pulse, specified as a positive scalar. Set the product of Pulse width (s) and Pulse repetition frequency to be less than or equal to one. This restriction ensures that the pulse width is smaller than the pulse repetition interval. Units are in seconds.

Example: 300e-6

Specify PRF as — Source of PRF value

Property (default) | Auto | Input port

Source of PRF value for the stretch processor, specified as Property, Auto, or Input port. When set to Property, the Pulse repetition frequency (Hz) parameter sets the PRF. When set to Input port, pass in the PRF using the PRF input port. When set to Auto, PRF is computed from the number of rows in the input signal.

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Pulse repetition frequency (Hz) — Pulse repetition frequency

1e4 (default) | positive scalar

Pulse repetition frequency, PRF, specified as a positive scalar. Units are in Hertz. Set this parameter to the same value set in any Waveform library block used in the simulation.

Dependencies

To enable this parameter, set the Specify PRF as parameter to Property.

FM sweep slope (Hz/s) — Slope of linear FM sweep

2e9 (default) | scalar

Slope of the linear FM sweeping as a scalar, specified as a scalar. Units are in Hertz per second.

Example: 1e3

FM sweep interval — Direction of FM sweep

Positive (default) | Symmetric

FM sweep interval, specified as Positive or Symmetric. If you set this parameter value to Positive, the waveform sweeps the frequency bandwidth between 0 and B, where B is the frequency bandwidth. If you set this parameter value to Symmetric, the waveform sweeps in the interval between –B/2 and B/2.

Signal 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

Reference range (m) — Center of ranges of interest

5000 (default) | positive scalar

Center of ranges of interest, specified as a positive scalar. The reference range must be within the unambiguous range of one pulse. Units are in meters.

Example: 10e3

Reference span (m) — Span of ranges of interest

500 (default) | positive scalar

Span of ranges of interest, specified as a positive scalar. The span of ranges is centered on the range specified by the Reference range (m) parameter. Units are in meters.

Example: 1e3

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 R2014b