FMCW Waveform
Frequencymodulated continuous (FMCW) waveform source
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
Port_1 — FMCW Waveform
complexvalued column vector
FMCW waveform, returned as a complexvalued 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 toTriangle
each sweep is onehalf period in duration.
Parameters
Sample rate (Hz) — Sample rate of the output waveform
1e6
(default)  positive scalar
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 
Sweep time (s) — Duration of each linear FM sweep
1e4
(default)
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.
Sweep bandwidth (Hz) — FM sweep bandwidth
1e5
(default)
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.
Sweep direction — FM sweep direction
Up
(default)  Down
 Triangle
Specify the direction of the linear FM sweep as one of
Up
, Down
, or
Triangle
.
Sweep interval — Location of FM sweep interval
Positive
(default)  Symmetric
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.
Output signal format — Output signal format
Sweeps
(default)  Samples
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 onehalf of a
period.
Number of samples in output — Number of samples in output
100
(default)  positive integer
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
Number of sweeps in output — Number of sweeps in output
1
(default)
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
.
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
See Also
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