Re: [USRP-users] Phase drift issue of N310
On 03/18/2019 01:26 PM, Damon wrote: Hi Marcus, Sorry, I can't reproduce the first observation in this discussion thread. A new problem about phase response has arisen. I am testing the phase coherence performance of four receiving channels of N310. A B200 is transmitting single tone continuous wave to a one to four splitter. The 4 outputs of the splitter are connected to 4 RX channels of N310. Attached please find the GRC file of this test. The RX frequency of 4 channels of N310 is set to 460MHz, and keep running in the test. The TX frequency of B200 is set to 460.02MHz first, and then to 460.03MHz. I thought the phase difference between different dboards would change very little when the signal frequency difference is very small, similar to the performance of X310. However, the fact is that the phase difference between the two dboards of N310 varies considerably with the signal frequency transmission. For example, in the attached picture, when the signal frequency is 460.01MHz, the phase difference between channel 2 and channel 0 is -118 degrees, the phase difference between channel 1 and channel 0 is 0 degrees; when the transmission frequency is adjusted to 460.03MHz, the phase difference between channel 2 and channel 0 is 117 degrees, and the phase difference between channel 1 and channel 0 is 0 degrees. It is very difficult to understand that the phase difference of two receiving channels of two different dboards has changed by 235 degrees with the signal frequency change of 20 KHz. The phase difference of two receiving channels of the same dboard is basically unchanged. Best regards, Damon Since the LO on the daughterboards has no idea that you've changed input frequency, this is clearly a measurement thing, and it's up to you to understand what you're measuring, and why. On 2019/3/16 上午7:47, Marcus D. Leech wrote: On 03/14/2019 04:37 PM, Damon wrote: Hi Marcus, The UHD Version is v3.14.0.0-rc1. Best regards, Damon I don't see this issue at all, using v3.14.0.0-rc3 How are you measuring phase, what does you flow-graph look like? Have you increased the gain enough to assure that the inherent system noise is not dominating your phase measurements? Hi Ali, The daughterboards have their own clock generators, but they are not exactly 'independent'. At least they don't have to be, as they share the same reference clock. Look at the block diagram: https://kb.ettus.com/images/9/9d/USRP_N310_N300_DB_Schematic.pdf and "Ref Clock" block. I don't have N310 and I know that reality can be a bit far from expectations (i.e. look at my "What makes sense and what doesn't in the way carrier frequency is set for TwinRX currently?" post). But maybe the daughterboards can be configured to use that reference clock. Best Regards, Piotr Krysik The LMK clock generator uses the reference clock from the mainboard, so there should not be any mutual phase-jitter/drift issues. I can test this on my N310 in the coming day or two. What version of UHD is in use? ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Phase drift issue of N310
Same Daughterboard is same LO, right, so things should be exactly the same on ch0-ch1 and ch2-ch3... -Original Message- From: USRP-users On Behalf Of Damon via USRP-users Sent: Monday, March 18, 2019 1:26 PM To: Marcus D. Leech ; usrp-users@lists.ettus.com Cc: Damon Qiu Subject: Re: [USRP-users] Phase drift issue of N310 *** WARNING *** EXTERNAL EMAIL -- This message originates from outside our organization. Hi Marcus, Sorry, I can't reproduce the first observation in this discussion thread. A new problem about phase response has arisen. I am testing the phase coherence performance of four receiving channels of N310. A B200 is transmitting single tone continuous wave to a one to four splitter. The 4 outputs of the splitter are connected to 4 RX channels of N310. Attached please find the GRC file of this test. The RX frequency of 4 channels of N310 is set to 460MHz, and keep running in the test. The TX frequency of B200 is set to 460.02MHz first, and then to 460.03MHz. I thought the phase difference between different dboards would change very little when the signal frequency difference is very small, similar to the performance of X310. However, the fact is that the phase difference between the two dboards of N310 varies considerably with the signal frequency transmission. For example, in the attached picture, when the signal frequency is 460.01MHz, the phase difference between channel 2 and channel 0 is -118 degrees, the phase difference between channel 1 and channel 0 is 0 degrees; when the transmission frequency is adjusted to 460.03MHz, the phase difference between channel 2 and channel 0 is 117 degrees, and the phase difference between channel 1 and channel 0 is 0 degrees. It is very difficult to understand that the phase difference of two receiving channels of two different dboards has changed by 235 degrees with the signal frequency change of 20 KHz. The phase difference of two receiving channels of the same dboard is basically unchanged. Best regards, Damon On 2019/3/16 上午7:47, Marcus D. Leech wrote: > On 03/14/2019 04:37 PM, Damon wrote: >> Hi Marcus, >> >> The UHD Version is v3.14.0.0-rc1. >> >> Best regards, >> >> Damon >> > I don't see this issue at all, using v3.14.0.0-rc3 > > How are you measuring phase, what does you flow-graph look like? Have > you increased the gain enough to assure that the inherent system > noise is not dominating your phase measurements? > > Hi Ali, The daughterboards have their own clock generators, but they are not exactly 'independent'. At least they don't have to be, as they share the same reference clock. Look at the block diagram: https://kb.ettus.com/images/9/9d/USRP_N310_N300_DB_Schematic.pdf and "Ref Clock" block. I don't have N310 and I know that reality can be a bit far from expectations (i.e. look at my "What makes sense and what doesn't in the way carrier frequency is set for TwinRX currently?" post). But maybe the daughterboards can be configured to use that reference clock. Best Regards, Piotr Krysik >>> The LMK clock generator uses the reference clock from the mainboard, so >>> there should not be any mutual phase-jitter/drift issues. I can >>> test this >>> on my N310 in the coming day or two. >>> >>> What version of UHD is in use? >> > > ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] E310 IMU
As usual, I should have emailed days ago since I found the answer just afterwards. Using the code from here: https://github.com/kriswiner/MPU9150/blob/master/MPU9150BasicAHRS.ino I was able to get good values. q[0] is w in his equation. From: Jason Matusiak Sent: Monday, March 18, 2019 12:40 PM To: Ettus Mail List Subject: E310 IMU I've started playing with the E310's IMU and I keep seeming to go around in circles. All I really want is a heading. I have my own app that is heavily borrowed from the RTIMULibDemo included on the device (and from github), but I can't seem to get the heading still right when dealing with the quaternions (and I've googled a 100 different things and never seem to get the right answers when I try their equations). I am sure I am making some small thing overly complicated, but I have been stuck for a couple of days now. The frustrating thing is that if I plot in wolframalpha (say "draw .646-.258i-.675j-.233k as a rotation operator"), the plot perfectly mimics what I was doing with the E310 when I captured that data. So trying to figure out how to determine that I have a heading 45 degrees off of North in that dataset is beyond me. Anyone played with the E310 IMU stuff further? ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] E310 IMU
I've started playing with the E310's IMU and I keep seeming to go around in circles. All I really want is a heading. I have my own app that is heavily borrowed from the RTIMULibDemo included on the device (and from github), but I can't seem to get the heading still right when dealing with the quaternions (and I've googled a 100 different things and never seem to get the right answers when I try their equations). I am sure I am making some small thing overly complicated, but I have been stuck for a couple of days now. The frustrating thing is that if I plot in wolframalpha (say "draw .646-.258i-.675j-.233k as a rotation operator"), the plot perfectly mimics what I was doing with the E310 when I captured that data. So trying to figure out how to determine that I have a heading 45 degrees off of North in that dataset is beyond me. Anyone played with the E310 IMU stuff further? ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] Fwd: [Discuss-gnuradio] European GNU Radio Days contribution deadline (March 21st)
Forwarded Message Subject: [Discuss-gnuradio] European GNU Radio Days contribution deadline (March 21st) Date: Mon, 18 Mar 2019 10:50:51 + From: jean-michel.fri...@femto-st.fr To: discuss-gnura...@gnu.org The European GNU Radio Days contribution deadline is getting close (set to March 21st). Please consider contributing if you wish to share the results of your work either as oral presentation, demonstration or tutorial. The template and submission site are available at https://gnuradio-fr-19.sciencesconf.org/ Contributions will be published on the GRCon Proceeding web site at https://pubs.gnuradio.org See you there, Jean-Michel -- JM Friedt, FEMTO-ST Time & Frequency/SENSeOR, 26 rue de l'Epitaphe, 25000 Besancon, France ___ Discuss-gnuradio mailing list discuss-gnura...@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Phase after Freq Hopping
Hi, why do you need to know/define the absolute phase of the transmitted signal? Phase is always relative to something. When impleneting a radar, you transmit a signal with an unknwon (absolute) phase. But this is not a problem, because after reception you will somehow correlate the transmitted with the received signal. In FMCW for example you multiply both signals, and get only the relative phase between transmitted and received signal - and that is the only thing you are interested in. I don't know how this works in OFDM, but you probably have to correlate the transmitted with the received signal and this will reveal the relative phase between both signals. Hope that helps, Fabian Am 18.03.2019 um 11:29 schrieb Patscheider, Dominik via USRP-users: Hey, What I wanted to achieve is a stepped OFDM Radar. To increase the baseband for the radar, I´m splitting the subcarrier and transmit them on four center frequencies. Thus it sends the first symbols on f0 (with an initial phase); afterwards increasing the center freq to f1 and transmit the next symbols,... And obviously the initial phase is changing after reconfiguring the frequency. If phase1, phase5, phase9,... phase2,phase6,... isn´t the same, it´s not possible to measure any velocity. Secondly, the time commands to change the freq I knew but didn´t use right now. Hope this explanation was useful to understand me and thanks for helping :) Dominik -Ursprüngliche Nachricht- Von: USRP-users Im Auftrag von Piotr Krysik via USRP-users Gesendet: Freitag, 15. März 2019 14:52 An: usrp-users@lists.ettus.com Betreff: Re: [USRP-users] Phase after Freq Hopping W dniu 12.03.2019 o 17:49, Patscheider, Dominik via USRP-users pisze: Hello , For a Radar I´m transmitting and receiving with the USRP X310 samples on different frequency steps. For instance, after 4 frames I´m coming back to the first center freq and continue this a few times. Hope the following description helps… f3 |phase4| |…| f2 |phase3| |…| f1 |phase2| |phase6| … f0 |phase1| |phase5| t --> According to the freq adjust every frame starts with a new phase. Phase 1 ≠Phase 5 Is there any possibility to get the same phase after returning to the same center freq? Phase 1=Phase 5, Phase 2 = Phase 6,… Hi Dominik, Can you describe what you want to achieve exactly? Probably you need to know phase relations because you want to do coherent processing of the signal. But from your description I don't know: -why on your ASCII art the signals transmitted on different frequencies seems to be overlapped? -which you part of it you want to process coherently? I also often use USRPs for radar transmissions. Issues with predicting initial phase difference of the received signal, in relation to digital waveform that is being transmitted, are much easier to overcome when you use timed commands to set the frequencies on Rx and Tx side synchronously (if you use UBX or SBX daughter-boards). Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Phase after Freq Hopping
Hi Dominik W dniu 18.03.2019 o 10:49, Patscheider, Dominik pisze: > Hi Piotr Krysik, > > I wanted to achieve an stepped OFDM Radar. > To increase the baseband for the radar, I´m splitting the subcarrier and > transmit them on four center frequencies. > Thus it sends the first symbols on f0 (with an initial phase); afterwards > increasing the center freq to f1 and transmit the next symbols,... > And obviously the initial phase is changing after reconfiguring the > frequency. If phase1, phase5, phase9,... phase2,phase6,... isn´t the same, > it´s not possible to measure any velocity. If you can predict what USRP does with phase differences of the received signal in relation to digital waveform, then you can compensate for it by shifting phases of the received or transmitted signal. > Secondly, the time commands to change the freq I knew but didn´t use right > now. > > I doubt what you are trying to do (keeping knowledge of phase relations after retuning analog RF front-end) can be done on USRPs without timed commands and appropriate daughter-board. -- Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
Re: [USRP-users] Phase after Freq Hopping
Hey, What I wanted to achieve is a stepped OFDM Radar. To increase the baseband for the radar, I´m splitting the subcarrier and transmit them on four center frequencies. Thus it sends the first symbols on f0 (with an initial phase); afterwards increasing the center freq to f1 and transmit the next symbols,... And obviously the initial phase is changing after reconfiguring the frequency. If phase1, phase5, phase9,... phase2,phase6,... isn´t the same, it´s not possible to measure any velocity. Secondly, the time commands to change the freq I knew but didn´t use right now. Hope this explanation was useful to understand me and thanks for helping :) Dominik -Ursprüngliche Nachricht- Von: USRP-users Im Auftrag von Piotr Krysik via USRP-users Gesendet: Freitag, 15. März 2019 14:52 An: usrp-users@lists.ettus.com Betreff: Re: [USRP-users] Phase after Freq Hopping W dniu 12.03.2019 o 17:49, Patscheider, Dominik via USRP-users pisze: > > Hello , > > > > For a Radar I´m transmitting and receiving with the USRP X310 samples > on different frequency steps. > > > > For instance, after 4 frames I´m coming back to the first center freq > and continue this a few times. Hope the following description helps… > > > > f3 |phase4| |…| > > f2 |phase3| |…| > > f1 |phase2| |phase6| … > > f0 |phase1| |phase5| > > t --> > > According to the freq adjust every frame starts with a new phase. > > Phase 1 ≠Phase 5 > > > > Is there any possibility to get the same phase after returning to the > same center freq? Phase 1=Phase 5, Phase 2 = Phase 6,… > > > > Hi Dominik, Can you describe what you want to achieve exactly? Probably you need to know phase relations because you want to do coherent processing of the signal. But from your description I don't know: -why on your ASCII art the signals transmitted on different frequencies seems to be overlapped? -which you part of it you want to process coherently? I also often use USRPs for radar transmissions. Issues with predicting initial phase difference of the received signal, in relation to digital waveform that is being transmitted, are much easier to overcome when you use timed commands to set the frequencies on Rx and Tx side synchronously (if you use UBX or SBX daughter-boards). Best Regards, Piotr Krysik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
