Hi Rob, coherent RX was working with 3.14.1.1 and even earlier versions. I just looked up the relevant commit: https://github.com/EttusResearch/fpga/commit/0b2364653405612a6d5dfaa0e69b1c6798771e6d#diff-7b9e54d62074f8f6c56a98e5ec1dd78d It seems that only DUC was fixed, which would mean the changelog (and even the commit headline) are misleading.
Robert From: Rob Kossler [mailto:rkoss...@nd.edu] Sent: Tuesday, February 18, 2020 5:22 PM To: Pöhlmann, Robert Cc: Nate Temple; sammywelsc...@gmail.com; usrp-users Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX Hi Robert, Thanks for the follow up. One question I have is related to your comment that you needed 3.15 for Tx but you didn't mention a version requirement for Rx. In my own tests, I found that I had to use 3.15 even for Rx or else I would get varying phase behavior. If you are able to get constant results with say 3.14.1.1, then I wonder if perhaps I had something else wrong and fooled myself into thinking that the UHD version fixed my issue. Rob On Tue, Feb 18, 2020 at 8:17 AM <robert.poehlm...@dlr.de<mailto:robert.poehlm...@dlr.de>> wrote: Hi Nate, Rob, Sammy, thanks for pointing out that the external LO should be set to 5 GHz for the QEC init calibration. So far I had omitted this calibration, as it wasn’t workin. This is important, please add it to the documentation (maybe it’s there and I missed it?). Happy to share some of our experiences regarding coherent operation of the N310: We are successfully using the N310 with coherent RX for DoA estimation. Our setup is: - external LO with 4-way splitter -> 2 TX 2 RX LO inputs - tracking_cals=OFF - At the beginning we run a flowgraph with force_reinit=1 and the desired init_cals settings - Later we use exactly the same settings without force_reinit, this ensures that no reinit is performed - The RX phase offset between the 4 channels is now constant, running different GnuRadio flowgraphs is no problem - When the device is power-cycled or a full re-init is performed, the phase of the radios can jump by 180° Very recently we added coherent TX, aiming at TX beamforming. Not much experience yet, but it seems to work. - Same setup as above. - Important: UHD 3.15.0.0 is required, some DUC bug has been fixed with this release - TX phase appears to be stable until power-cycle / re-init This even works with RFNoC (the RX part, TX not tested yet), although quite some modifications are necessary to gr-ettus to get synchronized streams. Regards, Robert From: USRP-users [mailto:usrp-users-boun...@lists.ettus.com<mailto:usrp-users-boun...@lists.ettus.com>] On Behalf Of Nate Temple via USRP-users Sent: Tuesday, January 28, 2020 9:03 PM To: Sammy Welschen Cc: usrp-users; Rob Kossler Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX Hi Sammy, >Can I turn it off and come back the next day and still have the same phase >offset between the channels that I had the day before? Yes. This assumes that you are running with the same frequency, gain, sample rate and system temperature that your calibrations were made with. Also unless you have phase stable cables, if you move your cables at all, it can cause phase variation. Regards, Nate Temple On Mon, Jan 27, 2020 at 9:29 AM Sammy Welschen <sammywelsc...@gmail.com<mailto:sammywelsc...@gmail.com>> wrote: Hi Nate, thank you for the information. I'm still a bit unsure what repeatable phase offset means exactly. Suppose I have a system with 8 channels with X310+TwinRX and shared LO. Can I turn it off and come back the next day and still have the same phase offset between the channels that I had the day before? Sammy Nate Temple via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> schrieb am Mo., 27. Jan. 2020, 18:04: Hi Rob, Robert, Sammy: Generally for this type of application we would recommend the X310+TwinRx. With the TwinRX, you'll be able to have repeatable phase offsets with a given gain, frequency, sample rate and temperature of a device/system. The N310 will have a 180 degree phase ambiguity due to the /2 LO architecture. It is possible to share the LO across multiple motherboards for a X310/Twin setup, and with the NI branded X310+TwinRX setup (NI-2955) the LO's are provided out of the back panel. The chassis for currently shipping and Rev C, F, G X310's back plate has the holes for the LO cables, but the sticker needs to be removed. This application note covers the process: https://kb.ettus.com/Modifying_an_X310_Chassis_for_External_LO_Sharing You'll also need to provide a splitter and most likely an inline amplifier to overcome splitter losses. A splitter such as the ZFRSC-4-842+ will work. https://www.minicircuits.com/pdfs/ZFRSC-4-842+.pdf @Rob: With the current init process of the N310, yes it is required to first set the external LO to 5 GHz. With regards to the offsets you're seeing, I believe you should only see a possible phase difference of 180* within the two channels on the same DB. Are you issuing a tune request at the start of streaming? Regards, Nate Temple On Mon, Jan 27, 2020 at 8:20 AM Rob Kossler via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: Robert, Sammy, I am presently running some tests which compare the X310/TwinRx and the N310 with regard to channel-to-channel phase. In my setup, I have a signal source that is split 8 ways (1:8 splitter) to feed the 4 channels of my TwinRx and 4 channels of my N310. I have seen some strange behavior of the N310 that perhaps Robert has experienced? Take a look: * For the TwinRx (for which I am a more experienced user with LO sharing), I get consistent channel-to-channel phase difference among all channels. This is true regardless of power cycles, re-starts of UHD, etc. * For the N310 (for which I am a beginner when it comes to external LO operation) * it seems more complex to run in this mode (as compared to TwinRx). In order to get it to work, I have had to disable startup QEC calibration because it seems that the N310 initial cal occurs at 2500 MHz RF such that I would need to have my external LO at 5000 MHz for startup (during the UHD deveice 'make') and then later switch my external LO to the desired RF*2. Is this true? * when I run with either external LO or internal LO, I see inconsistent channel-to-channel phase results even between the two channels of a given daughterboard that share the same LO. I do not understand how this is possible. My results over 16 captures (with some re-starts of UHD, device reboots, and switching between internal/external LO) show the following channel-to-channel phase difference between channels 0 and 1 which share the same LO: (values in degrees) -77, -19, -77, -19, -77, -19, -19, 39, -19, -19, -77, -19, -77, 39, -19, -19. Note that there are only 3 unique values and the delta happens to be 58 deg, but I don't know what that implies... Rob On Mon, Jan 27, 2020 at 9:57 AM Robert via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> wrote: With external LO its 300 MHz – 4 GHz, check footnote [3] from https://www.ettus.com/all-products/usrp-n310/. LO has to be supplied at twice the carrier freq. Currently we use 4 channels. You can find an example how to do the calibration here: https://github.com/EttusResearch/gr-doa gr-doa was written for TwinRX, but can be adapted. Phase noise behavior of N310 and N320/1 could be different, as N310 uses an RFIC and N32/1 use discrete components. This could be important if you want to operate in the small sample regime. From: USRP-users [mailto:usrp-users-boun...@lists.ettus.com<mailto:usrp-users-boun...@lists.ettus.com>] On Behalf Of Sammy Welschen via USRP-users Sent: Monday, January 27, 2020 3:40 PM To: usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com> Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX Thank you for the information Robert! Isn't it 6 GHz? However, 4 GHz would also be sufficient for me. How many channels does your system have? I suppose you use some algorithm for phase calibration after power cycling? I plan to do the same, so the 180 deg ambiguity should be manageable. I looked at the N32x, however, they cost twice as much and I dont't plan on using 200 MHz of bandwidth. If I have an external LO signal I can feed it to the N310, so the only difference between N310 and N32x in this regard would be that I need to generate the LO externally when using the N310, right? <robert.poehlm...@dlr.de<mailto:robert.poehlm...@dlr.de>> schrieb am Mo., 27. Jan. 2020, 14:42: We use the N310 for DoA estimation, however: - you are limited to 4 GHz - after power-cycling you get a 180° ambiguity between the two radios (I do not know if this could also happen when you just change the LO frequency) If you want to have >4 channels, have a look at the new N320/N321. No experience with those, but apparently they can do LO distribution. Also take into account if maybe later in the project you want to be able to transmit, which you cannot do with TwinRX. Regards, Robert From: USRP-users [mailto:usrp-users-boun...@lists.ettus.com<mailto:usrp-users-boun...@lists.ettus.com>] On Behalf Of Sammy Welschen via USRP-users Sent: Monday, January 27, 2020 2:19 PM To: usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com> Subject: Re: [USRP-users] DOA with N310 or X310+TwinRX Thank you Marcus! So the N310 would be the way to go? I was unsure since the TwinRX is recommended for phase coherent applications. Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com<mailto:usrp-users@lists.ettus.com>> schrieb am So., 26. Jan. 2020, 18:57: On 01/25/2020 11:43 AM, Sammy Welschen via USRP-users wrote: > Dear all, > > I am planning a system with 5-10 channels that is capable of DOA > estimation. > > Concerning the calibration of the resulting array, would there be a > difference between a system made up of N310 and one made up of X310 > with TwinRX boards? Would there be other important differences that > influence estimation performance? > > As I understand it, the TwinRX allows LO sharing between the boards in > a single X310, but this would not help me if I have two or three X310. > On the other hand, the N310s could be connected to a shared LO. > > Are the following thoughts correct? > > Suppose I turn on my system. Then I have to calibrate phase offsets > between channels in any case. Now I change the center frequency. If I > have N310s without shared LO, I have to recalibrate. Same for the > X310s, since LOs are shared only internally. If I have N310s with a > shared LO, I do not have to recalibrate. > > If I restart the system, I have to recalibrate in any case. > > The devices would by synchronized with PPS in any case and with the 10 > MHz reference if no external LO is used. > > What is the better choice for DOA estimation (N310 or X310 with TwinRX > or something different)? > > Thank you very much > > Sammy > > Sammy: Your characterization of the two scenarios is correct. There may be some folks on this list who have implemented DOA schemes, but likely few-to-none who have done it on both X310 and N310 and can comment on the differences they encountered. _______________________________________________ USRP-users mailing list USRP-users@lists.ettus.com<mailto: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<mailto: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<mailto: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<mailto:USRP-users@lists.ettus.com> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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