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.2
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.

fig.7
fig.8