Nonlinear FM Waveform

Signal generator with nonlinear frequency modulation.

nonlinear fm waveform

Description

The Nonlinear FM Waveform unit generates a nonlinear frequency modulated pulse signal with a specified pulse width, pulse repetition frequency (PRF) and frequency deviation. The signal at 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 parameter, 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 parameters to Pulses. Then select the check box for the Enable PRF output parameters.

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 Hz.

The ratio of the sampling frequency to the pulse repetition frequency (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 :

Usage in program code
Block parameters	`SampleRate`
Values	`positive scalar`
By default	`1e6`

Method to specify pulse duration - method to specify pulse duration
Pulse width (By default) | Duty cycle

Method to specify pulse duration as Pulse width or Duty cycle (two options are possible through time or fill factor, i.e. duty cycle):

Pulse width - the pulse width is set using the Pulse width (s) parameters.
Duty cycle - the pulse duration is calculated from the values of the parameters Pulse repetition frequency (Hz) and Duty Cycle.

Usage in program code
Block parameters	`PulseDuratiion`
Values	`string`
By default	`Pulse width`

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.

Usage in program code
Block parameters	`PulseWidth`
Values	`string`
By default	`50e-6`

Duty cycle - fill factor (duty cycle)
0.5 (by default) | scalar in the range [0,1]

Fill factor specified 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.

Usage in program code
Block parameters	`DutyCycle`
Values	`positive scalar`
* By default*	`0.5`

Pulse repetition frequency (Hz) - pulse repetition frequency
1e4 Hz (By default) | positive scalar

Pulse repetition frequency , specified as a scalar or string vector. The pulse repetition period is the inverse of the pulse repetition rate .

The Pulse repetition frequency (Hz) must meet the following constraints:

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) should be

be an integer. This condition expresses the requirement that the number of samples in one pulse repetition interval must be an integer.

Usage in program code
Block parameters	`PRF`
Values	`positive scalar`
By default	`1e4`

Frequency modulation - a type of non-linear frequency modulation
Polynomial (by default) | Hyperbolic | Hybrid Linear-Tangent | Stepped Price

A type of nonlinear frequency modulation.

Polynomial - the frequency of the signal at the block output is generated by a polynomial function. Coefficients of a polynomial are set by parameters Coefficients of a Polynomial FM. The resulting frequency function is normalised so that each pulse occupies the frequency bandwidth specified in the Sweep bandwidth (Hz) parameters. The Sweep interval parameter is inactive when the Frequency modulation parameter is set to Polynomial.
Hyperbolic - the unit generates a signal with hyperbolic frequency modulation. Use the Start frequency of a hyperbolic FM parameters to set the start frequency of a hyperbolic sweep. The Sweep interval parameters are inactive in this case.
Hybrid Linear-Tangent - the unit generates a hybrid waveform combining linear frequency modulation and tangent partial modulation. The balance between linear frequency modulation and tangent private modulation is set by the Balance between linear FM and tan-FM parameter, and the part of the curve used for tangent modulation law is set by the Tangent curve portion parameter.
Stepped Price - the block generates a stepped version of Price’s nonlinear frequency modulation. The Sweep interval parameter is inactive if the Frequency modulation parameter is set to Stepped Price. In this case, the frequency deviation is determined by the bandwidth factors set in the Bandwidth factors parameter and the number of steps set in the Number of frequency steps parameter.

Coefficients of a polynomial FM - coefficients of a polynomial function
[1 0 0] (by default) | ` real vector of length (N+1)`

Coefficients of the polynomial function of frequency change, given as a real vector of length (N+1).

The vector represents the coefficients of a polynomial of degree N. The first entry in the vector is the coefficient of the highest degree N polynomial. The last entry is the coefficient of the zero term of the polynomial.

*Example: [0.5,1,1,0.5]

Dependencies

To use this parameter, set the Frequency modulation parameters to Polynomial.

Sweep bandwidth (Hz) - frequency deviation
1e5 Hz (By default) | Positive scalar

The frequency deviation of a nonlinear frequency modulated signal specified as a positive scalar.

*Example: 1e3

Sweep direction - FM frequency deviation direction
Up (By default) | Down

Frequency deviation direction of the signal with nonlinear 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 between 0 and B, where B is the value of the Sweep bandwidth parameters.
Symmetric - the signal frequency will vary 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 Property is set, the offset is determined by the value of the Frequency Offset parameters.
If Input port is set, the offset is determined by the port value FreqOffset.

Usage in program code
Block parameters	`FreqOffsetSource`
Values	`Property` \| `Input port`
By default	`Property`

*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.

Usage in program code
Block parameters	`FreqOffset`
Values	`scalar`
By default	`0`

Output signal format - output signal format
Pulses (By default) | Samples

Output signal format specified as Pulses or Samples:

Samples - the output signal of the block, which has the form of a sequence of samples, the number of which is determined by the parameters Number of samples in output.
Pulses - the output signal of the block having the form of several pulses, the number of which is determined by the Number of pulses in output parameters.

Usage in program code
Block parameters	`OutSigForm` `Pulses` `Samples`
Values	`Pulses` \| `Samples`
By default	`Pulses`

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.

Usage in program code
Block parameters	`NumSamples`
Values	`positive number`
By default	`100`

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.

*Example: 2

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.

Usage in program code
Block parameters	`NumPulses`
Values	`positive number`
By default	`1`

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.

Usage in program code
Block parameters	`PRFOutport`
Values	`off` \| `on`
By default	`off`

Enable Matched Filter Coefficients Output - enable output of matched filter coefficients
disabled (by default) | enabled

Tick the checkbox to enable the Coeff output port.

Usage in program code
Block parameters	`CoeffOutport`
Values	`off` \| `on`
* By default*	`off`