FMCW Waveform

Frequency-modulated continuous (FMCW) waveform source

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  • FMCW Waveform block

Libraries:
Phased Array System Toolbox / Waveforms

Description

The FMCW Waveform block generates a frequency modulated continuous wave (FMCW) waveform with a specified sweep time and sweep bandwidth. The block output can be either an integer number of pulses or samples.

Ports

Output

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FMCW waveform, returned as a complex-valued column vector containing the waveform samples.

  • If the Output signal format parameter is set to Samples, then the output of the port consists of the number of samples set by the Number of samples in output parameter.

  • If the Output signal format parameter is set to Sweeps, then the output of the port consists of the number of sweeps set by the Number of sweeps in output parameter. Also, if the Sweep direction parameter is set to Triangle each sweep is one-half period in duration.

Parameters

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Sample rate of the output waveform, specified as a positive scalar. The ratio of Sample rate (Hz) to each element in the Pulse repetition frequency (Hz) vector must be an integer. This restriction is equivalent to requiring that the pulse repetition interval is an integral multiple of the sample interval.

Programmatic Use

Block Parameter:SampleRate
Type:double
Values:positive scalar
Default:1e6

Specify the duration, in seconds, of the upsweep or the downsweep of the signal as a scalar or row vector of positive, real numbers. The product of the Sample rate value and each Sweep time entry must be an integer.

To implement a varying sweep time, specify Sweep time as a row vector. The waveform uses successive entries of the vector as the sweep time for successive periods of the waveform. If the last element of the vector is reached, the process continues cyclically with the first entry of the vector.

If Sweep time and Sweep bandwidth are both row vectors, the vectors must have the same length.

If Sweep direction is Up or Down, the sweep period equals the sweep time. If Sweep direction is Triangle, the sweep period is twice the sweep time because each period consists of an upsweep segment and a downsweep segment.

Specify the bandwidth of the linear FM sweeping, in hertz, as a scalar or row vector of positive, real numbers.

To implement a varying bandwidth, specify Sweep bandwidth as a row vector. The waveform uses successive entries of the vector as the sweep bandwidth for successive periods of the waveform. If the waveform reaches the last element of the Sweep bandwidth vector, the process continues cyclically with the first entry of the vector.

If Sweep time and Sweep bandwidth are both row vectors, the vectors must have the same length.

Specify the direction of the linear FM sweep as one of Up, Down, or Triangle.

If you set this parameter value to Positive, the waveform sweeps in the interval between 0 and B, where B is the value of the Sweep bandwidth parameter. If you set this parameter to Symmetric, the waveform sweeps in the interval between –B/2 and B/2.

Specify the format of the output signal as Sweeps or Samples.

If you set this parameter to Sweeps, the output of the block is in the form of multiple sweeps. The number of sweeps is the value of the Number of sweeps in output parameter.

If you set this parameter to Samples, the output of the block is in the form of multiple samples. The number of samples is the value of the Number of samples in output parameter.

If the Sweep direction parameter is set to Triangle, each sweep is one-half of a period.

Number of samples in the block output, specified as a positive integer.

Example: 1000

Dependencies

To enable this parameter, set the Output signal format parameter to Samples.

Programmatic Use

Block Parameter:NumSamples
Type:double
Values:positive scalar
Default:100

Data Types: double

Specify the number of sweeps in the block output as a positive integer. This parameter appears only when you set Output signal format to Sweeps.

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 SimulationSimulation Behavior
NormalAcceleratorRapid Accelerator
Interpreted ExecutionThe block executes using the MATLAB interpreter.The block executes using the MATLAB interpreter.Creates a standalone executable from the model.
Code GenerationThe 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

See Also