IA, IB phase mismatch

#1

Hello,
The phase between I_A and I_B being acquired from the LMS seem to be in one of these three states:

  1. In phase
  2. 180 degrees out of phase
  3. Slightly off phase

There is also a reference to this issue in the post
https://discourse.myriadrf.org/t/lms7002m-180-degree-phase-jump/3331

Please advise,
Regards,

#2

Hello,
I have discovered this also. These appear to be two separate issues, the 180 degree phase jump is to do with the PLLs for the RF mixer stages and the small phase shift is due to some random delay. If you follow this link: Application for using the 2 RX channels simultaneously it provides examples of some software which is used on one of the SDR platforms to detect and correct this problem by testing the phase difference using internal RF loopback and correcting it by repeating resetting the problematic block. The method is rather crude but seems to work most of the time.

#3

Thanks for the reply @KMichaelides
I did read your post for this topic but I am still looking for a convincing explanation to the problem.
SXR is a single synthesizer for both the channels. How can a 180 degree phase jump occur between the two paths?
There has to be something “binary” in the path to effect this. In which case the solution also should be non-twisted.
What do you feel?

#4

I agree that according to the datasheet it is presented as a single PLL driving both channels, though I am not convinced, as the solution for the 180 degree flip is to reset the output divider of the PLL. Maybe this question should be directed to the manufacturer. I would be interested to know if this will be resolved with an updated SoC at any time in the future.

#5

Hello @Zack,
Looking forward to your inputs,
Regards,

#6

Hello @Zack,
Will greatly appreciate your help on this topic as well.
Regards,

#7

Hi @EnthuMan,

Check this document for more information, please.