29 July 2016

STANAG-4538, HDL+ BW7 waveforms

Bearing in mind the results and considerations about STANAG-4538 HDL+ protocol, as reported in the previous post, one can easily face the analysis of 3G-HF burst signals like this (fig. 1)

fig. 1
Once checked the headers and the length of the data sections, and found to be 288 symbols, I used the "harmonics" tool in order to get the modulations: I also used the zoom tool to better clarify the differences in each forward burst. A partial result at 8^ power is shown in figure 2: the PSK-8 harmonics due to BW6 headers are well visible, while the data sections (BW7) use different modulations according to the table of figure 3.

Fig. 3
 Analyzing all the forward bursts, it's possible identify the presence of the QAM-16 and QAM-64 BW7 waveforms, other than the PSK-8 BW6 waveform. 

fig. 4 - 4800 bps PSK-8 BW7 waveform
fig. 5 - 6400 bps BW7 QAM-16 waveform

fig. 6 - 9600/12800 bps BW7 QAM-64 waveform
It is worth noting in figs. 5,6 that the used constellations for QAM modulations are in 'circular rings' and then they are modified with respect to the standard ones.