If you want to read some TETRA-related bunkum, check out TETRA Watch. At least that particular page has two nice pictures of the waveform and spectrum!
|Frame length||255 symbols (56.7ms)|
- TETRA base station will always broadcast in each slot - if there is no information to transmit, slots are filled with the idle sequence.
- The first big peak at ~14ms is indicative of the repeating single-slot idle pattern that fills up all four slots (~56ms).
- Not sure what the peak at ~50.5ms is. If you do, let me know!
- A frequency-correction burst can be seen in the Scope Plot below.
The Fast Auto-correlation GUI block is used above.
Passing the baseband input into a constellation sink with the appropriate parameters results in:
This is also reflected in the eye diagram:
It should be noted that tuning plays an important role (at least with the follow setup) in ensuring a lock is maintained within the MPSK demodulator. Best results are found when tuning slightly off-centre of the (frequency domain) signal.