MODFM

Purpose:

Performs frequency modulation of a series.

Syntax:

MODFM(series, fmin, fmax)

series

-

A series, the input to modulate.

fmin

-

Optional, a real. The minimum modulation frequency. Defaults to 0.0.

fmax

-

Optional, a real. The maximum modulation frequency. Defaults to rate(series)/2.

Returns:

A series, the frequency modulated output.

Example:

W1: gtriwave(1000,.001, 4)

W2: modfm(w1)

W3: demodfm(w2)

W4: specgram(w2, 64, 63, 1024)

 

The triangle series of W1 is frequency modulated between 0 Hz and 500 Hz in W2. W3 recovers the modulated series and W4 displays the joint time-frequency plot of the frequency modulated series.

Example:

W1: gtriwave(1000,.001, 4)

W2: modfm(w1, 100, 300)

W3: demodfm(w2)

W4: specgram(w2, 64, 63, 1024)

 

Same as above except the series is frequency modulated between 100 Hz and 300 Hz.

Remarks:

A frequency modulated series is defined by:

 

image\modfm01.gif

 

where f(τ) is the modulating function.

 

The maximum modulation frequency, fmax, should be set to:

 

rate(series) / 2

 

or less.

 

See DEMODFM to demodulate a frequency modulated series.

 

See GSWEEP to generate a simple swept sinewave.

 

See MODAM to amplitude modulate a series.

See Also:

DEMODAM

DEMODFM

GSWEEP

MODAM

SPECGRAM