AX5243 PSK demodulation (non-180 degrees phase shifts)


I am currently attempting to demodulate a somewhat abnormal PSK signal with the AX5243, I find the documentation regarding PSK lacking, so I’ll try here.

I have seen table 21 in the Datasheet (also attached), as well as the description here on the forum (ref. KB: How to enable PSK modulation and control phase transitions on AX5043).

Specifically I would like to ask about the phase transitions always being 180 degrees.

The signal I am looking at is modulated at +/- 1rad, baud rate 400 bps Manchester encoded. Is that even possible and if so is there a more thorough description of the registers involved?

I do not know a whole lot about this area so there can potentially be a lot of stuff wrong with my setup, I have been monitoring the radiostate and rssi.
While the signal seems to be fine, I never pass the initial preamble state, which got me looking into the actual PSK modulation scheme in use and found that the phase is not applied as the AX5243 seems to expect.

Before throwing even more effort into debugging, it would be nice to know that it is at least possible to achieve - and perhaps a few pointers on where to look.

Kind regards

1 Like

Have you checked this blog Not Black Magic: AX5043 ?

Hi Adastra.

Thanks for your reply, I have visited that blog before, and it has already helped immensely to be honest.
Without him I would probably not have found the PSK forum post I linked in the initial post :slight_smile:

My impression is that he is using PSK in the “normal” sense - just as described in both the forum post and the data sheet. It may not be my only problem, but i cannot for the life of me figure out how to overcome that at least… and without overcoming that I have a hard time seeing how it can be achieved (if at all).

Oh well, does not look like I have much luck with this. Is it safe to assume then, that the AX5043/5243 can only utilize PSK modulation with 2 phases, 0 and 180 degrees?

I was somewhat hoping/expecting that a register was available for (re-)use to tweak the phases to some degree.

Hello ab1, I guess you are right. As they wrote in KB: How to enable PSK modulation and control phase transitions on AX5043 the phase transitions are always 180° and what can be controlled is just the direction of the jump (0° to 180° or 0° to -180° or alternating).