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I am attempting to modulate and then demodulate a vector with GFSK, but the output of the demodulation is very different from the original modulated vector. Any comments on what I am doing wrong?

The following is the flow graph I am using

This is the resulting QT graph

Thanks

Ina Sarhaye
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2 Answers2

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The output of GFSK demod block is in the format of "unpacked bytes", whereas the input to GFSK Mod is in "packed bytes", so when we try to compare the data before and after modulation, it does not come out to be the same. This can be seen in the following figure: enter image description here

To fix this issue, we need to convert the output of GFSK Demod into packed format. This can be done in any of the following two ways:

  1. Use the "Repack Bits" block after GFSK Demod with its endianness set to MSB.
  2. Use the "Pack K Bits" block after GFSK Demod with K = 8

enter image description here

By using the above mentioned methods, all of the input signals are matched in the QT GUI Time Plot: enter image description here

Mobi Zaman
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Gfsk mod takes packed bytes and gfsk demod outputs unpacked bytes (byte with only lsb containing data)

armleo
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