Hi, Thanks for the answers.I attach the Rx flowchart and grc of the frequency hopping. I have successfully used it on QO100 satellite. George SV1BDS
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Στις Πέμ, 27 Απρ, 2023 στις 14:57, ο χρήστηςMarcus
Müller<mmuel...@gnuradio.org> έγραψε: Hi George,
> Also I have implemented 1.000.000 hops/sec frequency hopping at QO100
> satellite, spread
> over 1 MHz, using 10240 different frequencies.
> Is this project of general interest?
Well, that's impossible to say, but honestly: it probably is! And also, you
shouldn't care
too much :) It's cool in any case!
My advise is: Just put it out there.
But I do have signal theory questions:
We know that if a signal has a bandwidth of 1 MHz, we can (complex) sample it
and contain
all its signal content with a sampling rate of 1 MS/s.
If you're doing a million hops per second, how are you achieving a bandwidth of
only 1
MHz? That means that every hop only gets a single sample, and you can't signify
"frequency" with just a single number.
So, I might have misunderstood you there, but it would seem what you claim to
have done is
mathematically not possible :(
> I create this script using Python to create QAM constellations points.
> May be of general interest.
It's nice, but GNU Radio already comes with that!
from gnuradio import digital
constellation = digital.constellation_16qam()
points = constellation.points()
(and you can just use digital.constellation_16qam().points() in a GRC block
parameter, no
need to build a string!)
These are also power-normalized to 1.
If you don't want normalized (or different sizes of) QAM constellation,
digital.qam.make_non_differential_constellation(M, gray_coded)
is your friend;
digital.qam.make_non_differential_constellation(4096, True)
makes a nice 4096-QAM, but it's average power isn't 1; you can fix that
points = digital.qam.make_non_differential_constellation(4096, True)
average_pwr = sum(point**2 for point in points) / len(points)
print(f"Average power: {average_pwr}; normalization factor hence:
{average_pwr**(-1/2)}")
normalized_points = [ point * average_pwr**(-1/2) for point in points ]
Similarly, since you're doing satellite communications, you might be interested
in PSKs,
an A-PSKs.
You can create a PSK using
digital.psk.psk_constellation(m=4, mod_code='gray', differential=True)
e.g.
digital.psk.psk_constellation(16, differential=False)
If you don't have GNU Radio but just python,
str([(i, j) for i in range(-n, n, 2) for j in range (-n, n, 2)])
does the same as your code, but might be a bit easier to read (again, if you
want to use
this in GRC, don't do the conversion to `str`; GRC accepts any valid Python in
its fields).
Best regards,
Marcus
FH_USBTESTRx.pdf
Description: Adobe PDF document
FH_USBTESTRx.grc
Description: Binary data
