I'm trying to analyse a signal from a HVAC remote control (864 MHz) with my HackRF, but I'm facing an interrogation about the used modulation:
- Is it BFSK (frequency modulation) or BPSK (phase modulation) ?
Here's what the signal looks like, once visualised from the HackRF raw data:
(with both I and Q waveforms, each one shifted from 90°)
NB: I can notice two different frequencies but sometimes it looks like both are shifted apart from 90° between transitions. Or maybe the ratio (bit width / modulation period) is really low in this example?
Here is a zoom on a part of the sample that gave me headaches:
EDIT: Like pointed out in the comments, the question was missing a lot of information and visualisation about the signal. Thanks for helping me guys... here is more:
Spectogram along time:
Zoom-in part of the first "symbols" with FFT, Amplitude, Phase and Frequency
FFT visualisation with max detection enabled (under GNU radio companion, with a DC blocker):
I've recorded the samples close to the signal frequency, I realised I might have done something wrong...
Constellation plot (under GNU radio companion, with a DC blocker):