Tagged: Estimating sweep speed
G4GUOParticipantG4GUO April 9, 2019 at 3:44 am
I am trying to identify interference to a satellite uplink. I have an IQ recording of it and it consists of 7 tones being swept upwards in frequency. Is there a way of using the Spike software to calculate the sweep rate of a signal.
Here is what the signal looks like in IQ playback (zoomed).
AndrewModeratorAndrew April 9, 2019 at 8:50 am
Not automatically, but could you use something like the FM vs Time plot in Zero span to calculate the time delta between the begin/end of the sweep, or maybe freq/sec? I set up a swept multi-tone signal here to try to recreate your signal. I added the FM vs Time plot plus the upcoming waterfall plot in zero-span (next release). In both plots you can see the sweep time and could calculate the sweep rate.
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G4GUOParticipantG4GUO April 9, 2019 at 10:58 am
It is not really strong enough to do the FM method.
I have thought of a crude way to do it I think.
use the single ‘step’ in zero span mode and count how many
steps it takes to cover a given frequency range. I assume it steps by the amount of samples in the playback box? Also what sample rate do the recording happen at 27 MS/s ?
I look forward to the waterfall feature !
AndrewModeratorAndrew April 9, 2019 at 12:20 pm
The sample rate at 27MHz is 40MS/s I/Q.
Yes, you are correct about the step size in the playback box.
Another alternative is to use the spectrum settings to control which part of the capture is shown in the spectrum plot. If you set the offset to two different values and then calculate freq/time you could get a sweep rate. We are making improvements to this as well in the next release which should simply this process even more.
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