GMSK vs. MSK

This model shows how to visually compare Gaussian minimum shift keying (GMSK) and minimum shift keying (MSK) modulation schemes.

Structure of the Example

The example model, doc_gmsk_vs_msk, includes these blocks:

Results and Displays

The example illustrates the difference between the two modulation schemes. The Eye Diagram blocks show the eye diagrams of the noisy GMSK and MSK signals.

The eye diagrams show the similarity between the GMSK and MSK signals when you set the Pulse length of the GMSK Modulator Baseband block to 1. Setting the Pulse length to 3 or 5 enables you to view the difference that a partial response modulation can have on the eye diagram. The number of paths increases, showing that the CPM waveform depends on values of the previous symbols as well as the present symbol. You can change the pulse length to 2 or 4, but you should change the Phase offset to pi/4 for a better view of the modulated signal. In order to more clearly view the Gaussian pulse shape, you must use scopes that enable you to view the phase of the signal, as described in the CPM Phase Tree example.