GFSK Demod

Hierarchical block for Gaussian Frequency Shift Key (GFSK) demodulation.

The input is the complex modulated signal at baseband.

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

Parameters

Samples/Symbol

Samples per baud >= 2 (integer)

Sensitivity

Given to the Quadrature Demod

Gain Mu

Controls rate of mu adjustment

Mu

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

Verbose

Print information about modulator?

Log

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.

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.

Source Files

Python files

[1]

Block definition

[2]