Agreed. The compensation part is not the one I worry about. What worries me the most is the angle-in-radians part.
Let's say that from the time sink plot I observe that I have pi/2 radians phase offset between channel 1 and channel 2. How do I know it's pi/2 radians and not -3pi/2? To be precise, I am also dumping the 2 channels complex data to 2 file sinks, which I then import on matlab for easier and faster experimentation. In other words, how can I precisely calculate the 4 discrete phase shifts I am observing in my application? Should I use cross correlation? Should I use Hilbert transform? I don't have a very noisy application, in case that plays a very crucial role. Thanks. On Jun 13, 2021 22:06, Marcus D Leech <patchvonbr...@gmail.com> wrote: Phase *correction* is easy once you know what that correction should be. Just a complex multiply-const by Complex(math.cos(angle-in-radians),math.sin(angle-in-radians)) Or the equivalent in complex exponential notation. Sent from my iPhone On Jun 13, 2021, at 1:52 PM, Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> wrote: Understandable. However, if you eventually hear anything about it please let me know. Can I contact you again tomorrow for some questions I have about the phase correction block I need to make? (I mean through discuss-gnuradio) Thank you very much. On Jun 13, 2021 19:37, Marcus D Leech <patchvonbr...@gmail.com> wrote: I haven’t heard fro R&D on it. Part of the problem is the N200 was designed over a decade ago, and the original engineering team have long since departed… Sent from my iPhone On Jun 13, 2021, at 6:25 AM, Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> wrote: Hi Marcus and sorry for bothering you again, but I'd like to ask if you have any news regarding my problem. Thank you. On Jun 11, 2021 16:15, Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> wrote: Yes it kind of helps, because if I manage to apply a phase shifting/correction technique, then all 4 scenarios could produce sensible data. I am trying to build a phase correction block now, that will compare the 2 received signals, to see which phase shift out of the possible 4, minimizes the absolute phase difference between the 2 channels. After I figure out which phase offset is the correct one, out of all 4, then I can run the rest of my DoA application. It is a bit of a pain in the a**, but it will have to do in case it never gets fixed. Let me know if you have any news from Ettus. Thanks again. ________________________________ From: Marcus D Leech <patchvonbr...@gmail.com> Sent: Friday, June 11, 2021 4:05 PM To: Skyvalakis Konstantinos Subject: Re: Phase Synchronize 2 USRP N200 w/ SBX cards Also does knowing that there are only 4 possible phase relationships help in your application at all? Like only one of the 4 possible phase assumptions can produce “sensible” data? Just a thought. Sent from my iPhone On Jun 11, 2021, at 9:03 AM, Marcus D Leech <patchvonbr...@gmail.com> wrote: I am an Ettus support contractor. I have a direct channel to R&D so I will relay any insights I receive here since any such feedback would be generally useful. Sent from my iPhone On Jun 11, 2021, at 8:15 AM, Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> wrote: I also tried contacting Ettus Support but they are not replying to my e-mails. I will try to implement the phase calibration for now. Thank you for your effort. ________________________________ From: Marcus D Leech <patchvonbr...@gmail.com> Sent: Friday, June 11, 2021 2:23 PM To: Skyvalakis Konstantinos Cc: Discuss-gnuradio@gnu.org Subject: Re: Phase Synchronize 2 USRP N200 w/ SBX cards I have a query in to Ettus R&D about possible causes. But you might need, for now to do an initial phase Calibration when you start up. Sent from my iPhone On Jun 11, 2021, at 3:39 AM, Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> wrote: I repeated the experiments once again today and I got once again the same results. I still keep on randomly getting these 4 cases I attached on a previous message. I observed that cases 1.png and 3.png have a phase difference of +/- 180 degrees and cases 2.png and 4.png also have a phase difference of +/- 180 degrees. Do you reckon you could help me any further with my problem? I really need to achieve this synchronization for my thesis. Thank you very much. ________________________________ From: Discuss-gnuradio <discuss-gnuradio-bounces+kskyvalakis=isc.tuc...@gnu.org> on behalf of Skyvalakis Konstantinos <kskyvala...@isc.tuc.gr> Sent: Friday, June 11, 2021 12:39 AM To: Marcus D. Leech Cc: Discuss-gnuradio@gnu.org Subject: Re: Phase Synchronize 2 USRP N200 w/ SBX cards Exactly my thoughts as well, I mean regarding the phase ambiguity of the WBX daughterboards, from what I've read on the Ettus website. I am 100% sure the daughterboards are SBX. On Jun 11, 2021 00:26, "Marcus D. Leech" <patchvonbr...@gmail.com> wrote: On 06/10/2021 01:00 PM, Skyvalakis Konstantinos wrote: In addition to my last message regarding the INTEGER_N tuning, I repeated the experiment multiple times. I even restarted the USRPs and the signal generator multiple times. What I observed was, that there were only 4 different recurring phase offsets (Blue = RX2 of SBX1, Red = RX2 of SBX2). I am attaching the 4 screenshots I captured. Thank you so much for your help. I feel like we're getting there. ________________________________ You're sure that you have SBX cards and not WBX cards? Sorry for the apparently-stupid question, but the WBX uses almost the same hardware as the SBX, but uses a 2XLO mixer that has fixed phase ambiguity--which would look like what you have here.
