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Signal Processing

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  • $\begingroup$ The constellation plot is made from the baseband, matched-filtered samples. If you have a passband signal, you'll have to downcovert it and filter it -- no way around that. $\endgroup$ Commented Apr 3, 2023 at 19:23
  • $\begingroup$ gotcha, the metafiles seem to imply that the signals are already at baseband (core:frequency : 0.0, unless I'm misinterpreting this value). Wouldn't this mean I could plot IvQ directly? $\endgroup$ Commented Apr 3, 2023 at 20:58
  • $\begingroup$ Not yet: as I mentioned, you very likely need to apply a matched filter (unless that has already been done), and then you need to perform symbol synchronization. In other words: the baseband signal is $s_\textrm{BB}(t) = \sum_k a_k p(t-kT)$, where the symbol rate is $1/T$ and $p(t)$ is the pulse shape. The constellation plot consists of the $a_k$ complex numbers; those need to be extracted from $s_\textrm{BB}(t)$. $\endgroup$ Commented Apr 3, 2023 at 21:24
  • $\begingroup$ The paper says: Each of these modulations are modulated with whitened random symbol data and in the case of single carrier modulations (other than GMSK) use a root-raised cosine (RRC) pulse shape filter. Based on your comment it seems that I would have to use a RRC for $p(t)$, but how could I figure out the symbol rate? $\endgroup$ Commented Apr 4, 2023 at 14:00
  • $\begingroup$ You could calculate it if know how many symbols are there in the signal, the sample rate, and the number of samples. Otherwise, no idea -- trial and error? The number of samples per symbol is usually between 2 and 8 or maybe 10. $\endgroup$ Commented Apr 4, 2023 at 16:01