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Chirp (FPScript)

21.09.2021

Calculates a swept-frequency cosine, i.e. a cosine signal with a variable frequency.

Syntax

Chirp(Time, Frequency1, Frequency2, Time2 [ , Operation = CHIRP_LINEAR ])

 

The syntax of the Chirp function consists of the following parts:

Part

Description

Time

A data set with the time for which the swept-frequency cosine is to be calculated.

All data structures are allowed. All numeric data types are permitted.

For complex data types the absolute value is formed.

If the argument is a list, then the function is executed for each element of the list and the result is also a list.

Frequency1

The frequency that the swept-frequency cosine is to have for Time = 0.

Permitted data structures are scalar value. All real data types are permitted.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

Frequency2

The frequency that the swept-frequency cosine is to have for the Time2 point in time.

Permitted data structures are scalar value. All real data types are permitted.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

Time2

The time for which the swept-frequency cosine is to have the Frequency2 frequency.

Permitted data structures are scalar value. All real data types are permitted.

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

Operation

Determines the type of frequency variation.

The argument Operation can have the following values:

Constant

Meaning

CHIRP_LINEAR

Linear frequency variation with the current frequency:

f(Time) = Frequency1 + (Frequency2 - Frequency1 ) / Time2 * Time

The following spectrogram shows the course of the current frequency:

CHIRP_QUADRATIC_CONCAVE

Quadratic concave frequency variation with the current frequency:

f(Time) = Frequency1 + (Frequency2 - Frequency1 ) / Time22 * Time2

Here, the vertex of the parabola is where Time = 0.

CHIRP_QUADRATIC_CONVEX

Quadratic convex frequency variation with the current frequency:

f(Time) = Frequency2 + (Frequency1 - Frequency2 ) / Time22 * (Time - Time2)2

Here, the vertex of the parabola is where Time = Time2.

CHIRP_EXPONENTIAL

Exponential frequency variation with the current frequency:

f(Time) = Frequency1 + exp(log(Frequency2 - Frequency1) / Time2 * Time)

If the argument is a list, then the first element in the list is taken. If this is also a list, then the process is repeated.

If this argument is omitted, it will be set to the default value CHIRP_LINEAR.

Remarks

The data type of the result is always 64-bit floating point.

The structure of the result corresponds to that of the argument Time. The calculation is done element-by-element where appropriate.

The result has the unit 1, if Time has a unit. Otherwise, it has no unit.

For aggregate data structures, only the Y component is considered and the X or, if applicable, Z component is copied into the result without modification.

Available in

FlexPro Basic, Professional, Developer Suite

Examples

Dim x = Series(0 s, 10 s, 0.001 s)
Signal(Chirp(x, 10 Hz, 0.1 kHz, x[-1]), x)
 

Generates a swept-frequency cosine signal with a sampling rate of 1 kHz in the time range from 0 s to 10 s with a linear frequency course from 10 Hz to 100 Hz.

See Also

Cos Function

Dirichlet Function

Integral Function

Sawtooth Function

Square Function

Straightline Function

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