MATLAB: How to set up an FSK model using the communication blockset to obtain a 2 tone signal

2-tonebasebandbaudfskm-fskmodulatorrateSignal Processing Toolbox

I would like to create a 1200 baud (Bell 202) modulation source using the communication blockset. I want a 2 tone signal, one at 1200 hz when a 1 is transmitted, the second is 2400 hz when a 0 is transmitted.

Best Answer

You can implement the FSK model by using a switch to select the source (binary '1' or binary '0'). Then feed the input to the 'M-FSK Modulator Baseband' block' setting the separating frequency as 1200Hz. You can view the response of the model by connecting Spectrum Scope.
See attached model for demonstration.
You can double click the switch to view the transitions between -600 Hz. and 600 Hz. This is because digital modulation is performed at baseband as detailed in the following URL:-
 <http://www.mathworks.com/help/releases/R2011a/toolbox/comm/ref/mfskdemodulatorbaseband.html>
You can modulate this baseband signal by 1800 Hz. to get the 1200 and 2400 FSK scheme.
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