GFSK Demod

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Revision as of 23:45, 23 August 2021 by Solomonbstoner (talk | contribs) (Make it clearer how users can replicate the results of the example flowgraph)
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Hierarchical block for Gaussian Minimum Shift Key (GFSK) demodulation.

The input is the complex modulated signal at baseband.

The output is a stream of bits packed 1 bit per byte (the LSB)


Samples per baud >= 2 (integer)
Given to the Quadrature Demod
Gain Mu
Controls rate of mu adjustment
Fractional delay [0.0, 1.0]
Omega Relative Limit
Sets max variation in omega (float, typically 0.000200 (200 ppm))
Freq Error
Bit rate error as a fraction
Print information about modulator?
Print modualtion data to files? (bool)

Example Flowgraph

The flowgraph below shows an example of the GFSK Mod and GFSK Demod blocks in action. We GFSK modulate 9-bit long bit stream '000111011', and then GFSK demodulate it. Then we compare the two bit streams to make sure that they are the same.

Gfsk mod and demod.png

When the flowgraph runs, we see that the red and blue signals are the same, meaning that the bit streams before and after the GFSK modulation and demodulation are the same.

In order to replicate the results shown below, make sure you do the following:

  1. Make sure you have a vector of 9 bits in your vector source. For example, I used (0,0,0,1,1,1,0,1,1) in this example.
  2. Make sure you turn off the unpack function in the GFSK Mod block. You will need to double click the block to bring up the Properties pop-up in order to turn it off. Turn it off. Then you will see "Unpack: Off" show up on the block after you close its Properties pop-up.

Gfsk mod and demod in action.png

Source Files

Python files
Block definition