gnuradiosoftware-defined-radio

What is the input Range for the osmocom Sink?

I'm using a HackRF One device and its corresponding osmocom Sink block inside of gnuradio-companion. Because the input to this block is Complex (i.e. a pair of Floats), I could conceivably send it an enormously large value. At some point the osmocom Sink will hit a maximum value and stop driving the attached HackRF to output stronger signals.

I'm trying to figure out what that maximum value is.

I've looked through the documentation at a number of different sites, for both the HackRF One and the osmocom source and can't find an answer. I tried looking through the source code itself, but couldn't see any clear indication there, although I may have missed something there. http://sdr.osmocom.org/trac/wiki/GrOsmoSDR

https://github.com/osmocom/gr-osmosdr

I also thought of deriving the value empirically, but didn't trust my equipment to get a precise measure of when the block started to hit the rails.

Any ideas? Thanks Friedman

Solution

  • I'm using a HackRF One device and its corresponding osmocom Sink block inside of gnuradio-companion. Because the input to this block is Complex (i.e. a pair of Floats), I could conceivably send it an enormously large value.

    No, the complexes z must meet

    |Re{z}|<=1

    |Im{z}|<=1

    because the osmocom sink/the underlying drivers and devices map that -1 – +1 range to the range of the I and Q DAC values.

    You're right, though, it's hard to measure empirically, because typically, the output amplifiers go into nonlinearity close to the maximum DAC outputs, and on top of that, everything is frequency-dependent, so e.g. 0.5+j0.5 at 400 MHz doesn't necessarily produce the same electrical field strength as 0.5+j0.5 at 1GHz.

    That's true for all non-calibrated SDR devices (which, aside from your typical multi-10k-Dollar Signal Generator, is everything, unless you calibrate for all frequencies of interest yourself).