Linear FM Waveform
Linear frequency modulated signal generator.
Description
The Linear FM Waveform unit generates a linear frequency modulated pulse signal with a specified pulse width, pulse repetition frequency (PRF) and frequency deviation. The output of the unit is an integer number of pulses or a sequence of samples.
Ports
Input
FreqOffset - frequency offset
scalar
Frequency offset specified as a scalar.
*Example: 2e3
Dependencies
To use this port, set the Source of Frequency Offset parameters to Input port.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Bool.
Output
Y - pulse signal
`complex vector
A signal at the block output specified as a complex vector.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Bool.
PRF - pulse repetition frequency
positive scalar
Pulse repetition rate specified as a positive scalar.
Dependencies
To use this port, set the Output signal format parameter to Pulses and then select the checkbox for the Enable PRF output parameter.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Bool.
Coeff - coefficients of the matched filter
vector | matrix
Coefficients of the matched filter given as a vector or matrix.
Dependencies
To use this port, select the Enable Matched Filter Coefficients Output checkbox.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64, Bool.
Parameters
Sample rate (Hz) - sampling rate
1e6 (by default) | positive scalar
The sampling frequency of the signal as a positive scalar. The unit of measurement is hertz.
The ratio of Sample rate (Hz) to the Pulse repetition frequency must be an integer.
This restriction is equivalent to requiring that the pulse repetition interval (PRI) be an integer multiple of the sampling step :
Method to specify pulse duration - pulse duration as time or fill factor (duty cycle)
Pulse width (By default) | Duty cycle
Method to specify pulse duration as Pulse width or Duty cycle:
-
Pulse width- the pulse width is set using the Pulse width (s) parameters. -
Duty cycle- fill factor, where the pulse width is calculated from the values of the parameters Pulse repetition frequency (Hz) and Duty Cycle.
Pulse width (s) - pulse width
50e-6 s (by default) | positive scalar
Pulse width , specified as a positive scalar value.
The product of Pulse width (s) and Pulse repetition frequency (Hz) must be less than or equal to one:
This constraint ensures that the pulse width is less than the pulse repetition period.
*Example: 300e-6
Dependencies
To use this parameter, set the Method to specify pulse duration parameters to Pulse width.
Duty cycle - fill factor (duty cycle)
0.5 (by default) | scalar in the range [0,1]
Fill factor set as a scalar in the range [0,1].
*Example: 0.7
Dependencies
To use this parameter, set the Method to specify pulse duration parameters to Duty cycle.
Pulse repetition frequency (Hz) - pulse repetition frequency
1e4 (By default) | positive scalar
Pulse repetition frequency (PRF) set as a scalar. The pulse repetition interval (PRI) is the inverse of the pulse repetition frequency (PRF).
The Pulse repetition frequency (Hz) must meet the following restrictions:
-
The product of Pulse width (s) and Pulse repetition frequency (Hz) must be less than or equal to one:
This constraint ensures that the pulse width is less than the pulse repetition period. For a phase encoded signal, the pulse width is equal to the product of the duration of one chip by the number of chips.
The ratio of Sample rate (Hz) to Pulse repetition frequency (Hz) must be an integer:
This restriction is equivalent to requiring that the number of samples in a pulse repetition period be an integer.
Sweep bandwidth (Hz) - spectrum width of the LFM signal
1e5 Hz (by default) | positive scalar
Double frequency deviation of the linear frequency modulated signal specified as a positive scalar.
*Example: 1e3
Sweep direction - frequency deviation direction
Up (By default) | Down
Frequency deviation direction of the signal with linear frequency modulation:
-
Up- frequency increase. -
Down- decreasing frequency.
Sweep interval - frequency deviation interval
Positive (By default) | Symmetric.
Frequency deviation interval specified as Positive or Symmetric:
-
Positive- the signal frequency will vary in the interval from0to B, where B is the value of the Sweep bandwidth parameters. -
Symmetric- the signal frequency will vary in the interval between −B/2 and B/2.
Envelope function - setting the envelope of the signal with frequency modulation
Rectangular (by default) | Gaussian
Envelope of the frequency modulated signal set as Rectangular or Gaussian.
Source of Frequency Offset - frequency offset setting
Property (By default) | Input port.
Frequency offset set as Property or Input port:
-
If
Propertyis set, the offset is determined by the value of the Frequency Offset parameters. -
If
Input portis set, the offset is determined by the port value FreqOffset.
Frequency Offset (Hz) - frequency offset
0 (By default) | scalar
Frequency offset set as a scalar.
*Example: 2e3
Dependencies
To use this parameter, set the Source of Frequency Offset parameter to Property.
Output signal format - output signal format
Pulses (by default) | Samples
Output signal format as Pulses or Samples:
-
If you set this parameter to
Pulses, the block output consists of a number of pulses. The number of pulses is the value of the Number of pulses in output parameter. -
If you set this parameter to
Samples, the block output consists of multiple samples. The number of samples is the value of the Number of samples in output parameter.
Number of samples in output - number of samples of the output signal
100 (by default) | `positive number `
The number of samples of the output signal specified as a positive integer.
*Example: 1000
Dependencies
To use this parameter, set the Output signal format parameters to Samples.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Number of pulses in output - number of pulses of the output signal
1 (by default) | positive number
The number of pulses of the output signal set as a positive integer.
Dependencies
To use this parameter, set the Output signal format parameters to Pulses.
Data types: Float16, Float32, Float64, Int8, Int16, Int32, Int64, UInt8, UInt16, UInt32, UInt64.
Enable PRF Output - enable PRF output
off (by default) | on.
Select the checkbox to enable the PRF output port.
Dependencies
To use this parameter, set the Output signal format parameters to Pulses.
Enable Matched Filter Coefficients Output - enable output of matched filter coefficients
off (by default) | on - enable
Tick the checkbox to enable the Coeff output port.