MATLAB: How are the frequencies chosen for mfsk using DMODCE

Question

I am using the function DMODCE for M-ary Frequency Shift keying. I do the following to obtain the output signal y:

y = dmodce(x,Fd,Fs,'fsk',M,tone)

I would like to know how the frequencies are picked for the modulation, and what the tone parameter represents.

The first frequency does not seem to be located at "tone", which is what I had expected from a baseband implementation.

Answer 1

The function DMODCE generates M tones centered around 0 Hz. The frequency separation between each pair of adjacent tones is the "tone" parameter.