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
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
Re: [USRP-users] Phase after Freq Hopping
I think it depends on what is meant by the “same phase as last time”. Relative to what? Sent from my iPhone > On Mar 14, 2019, at 10:17 AM, Sylvain Munaut <246...@gmail.com> wrote: > > Hi, > > integer-N tuning maybe ? > And use the DDC/DUC for the rest ? > > Cheers, > > Sylvain ___ 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, integer-N tuning maybe ? And use the DDC/DUC for the rest ? Cheers, Sylvain ___ 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
That kind would be cool ;) . But: since this is radar, the reason for all this is probably exceeding the Nyquist bw of the DAC with the radar wave form :( Cheers, Marcus On Tue, 2019-03-12 at 23:49 -0700, Ian Buckley via USRP-users wrote: > > On Mar 12, 2019, at 3:05 PM, Marcus D. Leech via USRP-users < > > usrp-users@lists.ettus.com> wrote: > > > > On 03/12/2019 12:49 PM, Patscheider, Dominik via USRP-users wrote: > > > 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,… > > > > > > Thanks in advance. > > > dominik > > > > > Almost certainly not. It would take a very special type of > > frequency synthesizer to achieve that. > > > You mean the sort of frequency synthesizer that might be implemented > entirely in the digital domain within say a DUC or DDC with the > ability to have a time coordinated update to the respective phase- > increment registers? :-) > ___ > 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
On 03/13/2019 02:49 AM, Ian Buckley wrote: You mean the sort of frequency synthesizer that might be implemented entirely in the digital domain within say a DUC or DDC with the ability to have a time coordinated update to the respective phase-increment registers? :-) Yes, within the analog bandwidth, digital-only tuning could achieve this. I was assuming that analog-tuning would be required, but perhaps not. ___ 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
> On Mar 12, 2019, at 3:05 PM, Marcus D. Leech via USRP-users > wrote: > > On 03/12/2019 12:49 PM, Patscheider, Dominik via USRP-users wrote: >> 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,… >> >> Thanks in advance. >> dominik >> > Almost certainly not. It would take a very special type of frequency > synthesizer to achieve that. > You mean the sort of frequency synthesizer that might be implemented entirely in the digital domain within say a DUC or DDC with the ability to have a time coordinated update to the respective phase-increment registers? :-)___ 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
On 03/12/2019 12:49 PM, Patscheider, Dominik via USRP-users wrote: 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,… Thanks in advance. dominik Almost certainly not. It would take a very special type of frequency synthesizer to achieve that. ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
[USRP-users] Phase after Freq Hopping
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,… Thanks in advance. dominik ___ USRP-users mailing list USRP-users@lists.ettus.com http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
