Hi everyone! I was wondering if anyone knew if it was possible to phase align more than 2 X310s (with UBX daughterboard) to form a coherent array? I know that 2x2 MIMO is possible using a single X310, but I want to be able to sync 4 of them. I thought I read somewhere that it was dependent on the daughterboard, but I can’t find that thread anywhere. Thanks for all the help! [Description: http://www.oceanit.com/sites/default/files/oceanit_sig.png] Sarah Tran Leony | Electrical Engineer 828 Fort Street Mall Suite 600 | Honolulu, HI 96813 Email: stran@oceanit.com<mailto:stran@oceanit.com> Office: 808.531.3017 x139 | Direct: 808.954.4105 Fax: 808.531.3177 | Mobile: 405.837.2614 Click ► Website<http://www.oceanit.com/> | Facebook<https://www.facebook.com/oceanit> | Twitter<http://twitter.com/oceanit> | LinkedIn<https://www.linkedin.com/company/oceanit> [Description: http://www.oceanit.com/sites/default/files/tree_sig.png]Please consider the environment before printing this message. NOTICE TO RECIPIENT: This message may contain confidential or privileged information and any unauthorized use, disclosure or copying of this message or its contents is prohibited. If you are not the intended recipient, please reply to advise the sender of the error and immediately delete this message and any attachments from your system.

On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: > > Hi everyone! > > I was wondering if anyone knew if it was possible to phase align more > than 2 X310s (with UBX daughterboard) to form a coherent array? I know > that 2x2 MIMO is possible using a single X310, but I want to be able > to sync 4 of them. I thought I read somewhere that it was dependent on > the daughterboard, but I can’t find that thread anywhere. > > Thanks for all the help! > Yes, use an external 10MHz reference and 1PPS source, like the Octoclock, or Octoclock-G, or similar. Also, see this App note: https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices > Description: http://www.oceanit.com/sites/default/files/oceanit_sig.png > > > > *Sarah Tran Leony**|*Electrical Engineer > > 828 Fort Street Mall Suite 600*|*Honolulu, HI 96813 > > Email: *_stran@oceanit.com <mailto:stran@oceanit.com>_* > > Office: 808.531.3017 x139*| *Direct: 808.954.4105 > Fax: 808.531.3177 *| *Mobile: 405.837.2614 > > > > *Click *►*Website* <http://www.oceanit.com/>***|**Facebook* > <https://www.facebook.com/oceanit>***|**Twitter* > <http://twitter.com/oceanit>***|**LinkedIn* > <https://www.linkedin.com/company/oceanit>** > > Description: > http://www.oceanit.com/sites/default/files/tree_sig.pngPlease consider > the environment before printing thismessage.** > > NOTICE TO RECIPIENT: This message may contain confidential or > privileged information and any unauthorized use, disclosure or copying > of this message or its contents is prohibited. If you are not the > intended recipient, please reply to advise the sender of the error and > immediately delete this message and any attachments from your system. > > > > _______________________________________________ > USRP-users mailing list > USRP-users@lists.ettus.com > http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

Sarah, I just happen to be in the middle of an evaluation presently of the channel-to-channel phase coherence among various 4 chan receivers, among them an X310/UBX (pair) and X310/TwinRx. For this test, I inject a CW tone (-48 dBm) into a 1:4 power divider which then feeds the four receiver channels. I then compute the cross correlation (in 1 msec blocks, zero lag) between each of channels 2-4 and channel 1 (arbitrarily selected as the reference channel). The following figure shows the channel-to-channel phase variation over a 2 sec window. The left plots are for the four channel X310/TwinRx. The right plots are for the pair of X310/UBX (appropriately synced). The 3 plots for each device show channels 2-4 in comparison to channel 1. Note that the TwinRx results show much smaller variation (as expected since there is a shared LO). Also note that for UBX results, the variation is much smaller for the two channels that are housed in the same X310 (top right plot). I suspect that the much larger variations shown for the 3rd and 4th channels (relative to channel 1) are related to a 10 MHz PLL circuit in each X310. Bottom line is that I see at least +/- 1 degree "wobble" in the channel-to-channel phase over time. You'll need to determine if this is acceptable for your application. Rob [image: Inline image 1] On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users < usrp-users@lists.ettus.com> wrote: > On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: > > Hi everyone! > > > > I was wondering if anyone knew if it was possible to phase align more than > 2 X310s (with UBX daughterboard) to form a coherent array? I know that 2x2 > MIMO is possible using a single X310, but I want to be able to sync 4 of > them. I thought I read somewhere that it was dependent on the > daughterboard, but I can’t find that thread anywhere. > > > > Thanks for all the help! > > Yes, use an external 10MHz reference and 1PPS source, like the Octoclock, > or Octoclock-G, or similar. > > Also, see this App note: > > https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices > > > > > > > > [image: Description: > http://www.oceanit.com/sites/default/files/oceanit_sig.png] > > *Sarah Tran Leony* *|* Electrical Engineer > > 828 Fort Street Mall Suite 600 *|* Honolulu, HI 96813 > > Email: *stran@oceanit.com <stran@oceanit.com>* > > Office: 808.531.3017 x139 <(808)%20531-3017> *| *Direct: 808.954.4105 > <(808)%20954-4105> > Fax: 808.531.3177 <(808)%20531-3177> *| *Mobile: 405.837.2614 > <(405)%20837-2614> > > > > *Click *► *Website* <http://www.oceanit.com/> *|* *Facebook* > <https://www.facebook.com/oceanit> *|* *Twitter* > <http://twitter.com/oceanit> *|* *LinkedIn* > <https://www.linkedin.com/company/oceanit> > > [image: Description: > http://www.oceanit.com/sites/default/files/tree_sig.png]Please consider > the environment before printing this message. > > NOTICE TO RECIPIENT: This message may contain confidential or privileged > information and any unauthorized use, disclosure or copying of this message > or its contents is prohibited. If you are not the intended recipient, > please reply to advise the sender of the error and immediately delete this > message and any attachments from your system. > > > > > > > _______________________________________________ > USRP-users mailing listUSRP-users@lists.ettus.comhttp://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 > >

 Sarah,
 I just happen to be in the middle of an evaluation presently of the channel-to-channel phase coherence among various 4 chan receivers, among them an X310/UBX (pair) and X310/TwinRx.  For this test, I inject a CW tone (-48 dBm) into a 1:4 power divider which then feeds the four receiver channels. I then compute the cross correlation (in 1 msec blocks, zero lag) between each of channels 2-4 and channel 1 (arbitrarily selected as the reference channel).  The following figure shows the channel-to-channel phase variation over a 2 sec window.  The left plots are for the four channel X310/TwinRx.  The right plots are for the pair of  X310/UBX (appropriately synced).   The 3 plots for each device show channels 2-4 in comparison to channel 1.  Note that the TwinRx results show much smaller variation (as expected since there is a shared LO).  Also note that for UBX results, the variation is much smaller for the two channels that are housed in the same X310 (top right plot).  I suspect that the much larger variations shown for the 3rd and 4th channels (relative to channel 1) are related to a 10 MHz PLL circuit in each X310.  Bottom line is that I see at least +/- 1 degree "wobble" in the channel-to-channel phase over time.  You'll need to determine if this is acceptable for your application.

 Rob


 [Inline image 1]


 On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com > wrote:

     On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote:

         Hi everyone!

          

         I was wondering if anyone knew if it was possible to phase align more than 2 X310s (with UBX daughterboard) to form a coherent array? I know that 2x2 MIMO is possible using a single X310, but I want to be able to sync 4 of them. I thought I read somewhere that it was dependent on the daughterboard, but I can’t find that thread anywhere.

          

         Thanks for all the help!

     Also, see this App note:

     https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices

         [Description:                       http://www.oceanit.com/sites/default/files/oceanit_sig.png]

         Sarah Tran Leony  |  Electrical Engineer

         828 Fort Street Mall Suite 600  |  Honolulu, HI 96813

         Email: stran@oceanit.com mailto:stran@oceanit.com

         Office: 808.531.3017 x139 | Direct: 808.954.4105
         Fax: 808.531.3177 | Mobile: 405.837.2614

          

         Click ► Website http://www.oceanit.com/  |  Facebook https://www.facebook.com/oceanit  |  Twitter http://twitter.com/oceanit  |  LinkedIn https://www.linkedin.com/company/oceanit

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         NOTICE TO RECIPIENT: This message may contain confidential or privileged information and any unauthorized use, disclosure or copying of this message or its contents is prohibited.  If you are not the intended recipient, please reply to advise the sender of the error and immediately delete this message and any attachments from your system.

          

          



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On the UBX results, Y0 -> Y1, I assume that is in the same motherboard? Y2 and Y3 on a different motherboard (delta seems to be much larger, but very very similar across Y2 and Y3 relative to Y0)? So if I wanted to improve on the "error" on channels 3 and 4 or add more channels, are there any options? Lets assume I have done the easy things like match cable lengths and use splitters with low phase balance etc. :) > On November 6, 2017 at 6:33 PM Rob Kossler via USRP-users <usrp-users@lists.ettus.com> wrote: > > Sarah, > I just happen to be in the middle of an evaluation presently of the channel-to-channel phase coherence among various 4 chan receivers, among them an X310/UBX (pair) and X310/TwinRx. For this test, I inject a CW tone (-48 dBm) into a 1:4 power divider which then feeds the four receiver channels. I then compute the cross correlation (in 1 msec blocks, zero lag) between each of channels 2-4 and channel 1 (arbitrarily selected as the reference channel). The following figure shows the channel-to-channel phase variation over a 2 sec window. The left plots are for the four channel X310/TwinRx. The right plots are for the pair of X310/UBX (appropriately synced). The 3 plots for each device show channels 2-4 in comparison to channel 1. Note that the TwinRx results show much smaller variation (as expected since there is a shared LO). Also note that for UBX results, the variation is much smaller for the two channels that are housed in the same X310 (top right plot). I suspect that the much larger variations shown for the 3rd and 4th channels (relative to channel 1) are related to a 10 MHz PLL circuit in each X310. Bottom line is that I see at least +/- 1 degree "wobble" in the channel-to-channel phase over time. You'll need to determine if this is acceptable for your application. > > Rob > > > [Inline image 1] > > > On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users <usrp-users@lists.ettus.com mailto:usrp-users@lists.ettus.com > wrote: > > > > On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: > > > > > > > > > > Hi everyone! > > > > > > > > > > > > I was wondering if anyone knew if it was possible to phase align more than 2 X310s (with UBX daughterboard) to form a coherent array? I know that 2x2 MIMO is possible using a single X310, but I want to be able to sync 4 of them. I thought I read somewhere that it was dependent on the daughterboard, but I can’t find that thread anywhere. > > > > > > > > > > > > Thanks for all the help! > > > > > > > > Yes, use an external 10MHz reference and 1PPS source, like the Octoclock, or Octoclock-G, or similar. > > > > Also, see this App note: > > > > https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > [Description: http://www.oceanit.com/sites/default/files/oceanit_sig.png] > > > > > > Sarah Tran Leony | Electrical Engineer > > > > > > 828 Fort Street Mall Suite 600 | Honolulu, HI 96813 > > > > > > Email: stran@oceanit.com mailto:stran@oceanit.com > > > > > > Office: 808.531.3017 x139 | Direct: 808.954.4105 > > > Fax: 808.531.3177 | Mobile: 405.837.2614 > > > > > > > > > > > > Click ► Website http://www.oceanit.com/ | Facebook https://www.facebook.com/oceanit | Twitter http://twitter.com/oceanit | LinkedIn https://www.linkedin.com/company/oceanit > > > > > > [Description: http://www.oceanit.com/sites/default/files/tree_sig.png]Please consider the environment before printing this message. > > > > > > NOTICE TO RECIPIENT: This message may contain confidential or privileged information and any unauthorized use, disclosure or copying of this message or its contents is prohibited. If you are not the intended recipient, please reply to advise the sender of the error and immediately delete this message and any attachments from your system. > > > > > > > > > > > > > > > > > > > > > > > > _______________________________________________ > > > 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 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 http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com > > > > > > > >

Yes, y0 and y1 on first motherboard, y2 and y3 on second motherboard. Unfortunately, I don't know of any options to improve it. Rob On Tue, Nov 7, 2017 at 11:28 AM, ROBIN TORTORA <tilla@comcast.net> wrote: > On the UBX results, Y0 -> Y1, I assume that is in the same motherboard? > > > Y2 and Y3 on a different motherboard (delta seems to be much larger, but > very very similar across Y2 and Y3 relative to Y0)? > > > So if I wanted to improve on the "error" on channels 3 and 4 or add more > channels, are there any options? > > > Lets assume I have done the easy things like match cable lengths and use > splitters with low phase balance etc. :) > > On November 6, 2017 at 6:33 PM Rob Kossler via USRP-users < > usrp-users@lists.ettus.com> wrote: > > Sarah, > I just happen to be in the middle of an evaluation presently of the > channel-to-channel phase coherence among various 4 chan receivers, among > them an X310/UBX (pair) and X310/TwinRx. For this test, I inject a CW tone > (-48 dBm) into a 1:4 power divider which then feeds the four receiver > channels. I then compute the cross correlation (in 1 msec blocks, zero lag) > between each of channels 2-4 and channel 1 (arbitrarily selected as the > reference channel). The following figure shows the channel-to-channel > phase variation over a 2 sec window. The left plots are for the four > channel X310/TwinRx. The right plots are for the pair of X310/UBX > (appropriately synced). The 3 plots for each device show channels 2-4 in > comparison to channel 1. Note that the TwinRx results show much smaller > variation (as expected since there is a shared LO). Also note that for UBX > results, the variation is much smaller for the two channels that are housed > in the same X310 (top right plot). I suspect that the much larger > variations shown for the 3rd and 4th channels (relative to channel 1) are > related to a 10 MHz PLL circuit in each X310. Bottom line is that I see at > least +/- 1 degree "wobble" in the channel-to-channel phase over time. > You'll need to determine if this is acceptable for your application. > > Rob > > > [image: Inline image 1] > > > On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users < > usrp-users@lists.ettus.com> wrote: > > On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: > > Hi everyone! > > > > I was wondering if anyone knew if it was possible to phase align more than > 2 X310s (with UBX daughterboard) to form a coherent array? I know that 2x2 > MIMO is possible using a single X310, but I want to be able to sync 4 of > them. I thought I read somewhere that it was dependent on the > daughterboard, but I can’t find that thread anywhere. > > > > Thanks for all the help! > > Yes, use an external 10MHz reference and 1PPS source, like the Octoclock, > or Octoclock-G, or similar. > > Also, see this App note: > > https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices > > > > > > > > > > [image: Description: > http://www.oceanit.com/sites/default/files/oceanit_sig.png] > > *Sarah Tran Leony* *|* Electrical Engineer > > 828 Fort Street Mall Suite 600 > <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g> > *| > <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>* > Honolulu, HI 96813 > <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g> > > Email: *stran@oceanit.com <stran@oceanit.com>* > > Office: 808.531.3017 x139 *| *Direct: 808.954.4105 > Fax: 808.531.3177 *| *Mobile: 405.837.2614 > > > > *Click *► *Website* <http://www.oceanit.com/> *|* *Facebook* > <https://www.facebook.com/oceanit> *|* *Twitter* > <http://twitter.com/oceanit> *|* *LinkedIn* > <https://www.linkedin.com/company/oceanit> > > [image: Description: > http://www.oceanit.com/sites/default/files/tree_sig.png]Please consider > the environment before printing this message. > > NOTICE TO RECIPIENT: This message may contain confidential or privileged > information and any unauthorized use, disclosure or copying of this message > or its contents is prohibited. If you are not the intended recipient, > please reply to advise the sender of the error and immediately delete this > message and any attachments from your system. > > > > > > > _______________________________________________ > USRP-users mailing listUSRP-users@lists.ettus.comhttp://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 > > >

 On the UBX results, Y0 -> Y1, I assume that is in the same
 motherboard?


 Y2 and Y3 on a different motherboard (delta seems to be much
 larger, but very very similar across Y2 and Y3 relative to Y0)?


 So if I wanted to improve on the "error" on channels 3 and 4 or
 add more channels, are there any options?


 Lets assume I have done the easy things like match cable lengths
 and use splitters with low phase balance etc. :)

 On November 6, 2017 at 6:33 PM Rob Kossler via USRP-users
 <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
 wrote:

 Sarah,
 I just happen to be in the middle of an evaluation presently of
 the channel-to-channel phase coherence among various 4 chan
 receivers, among them an X310/UBX (pair) and X310/TwinRx.  For
 this test, I inject a CW tone (-48 dBm) into a 1:4 power divider
 which then feeds the four receiver channels. I then compute the
 cross correlation (in 1 msec blocks, zero lag) between each of
 channels 2-4 and channel 1 (arbitrarily selected as the reference
 channel).  The following figure shows the channel-to-channel
 phase variation over a 2 sec window.  The left plots are for the
 four channel X310/TwinRx.  The right plots are for the pair of 
 X310/UBX (appropriately synced).   The 3 plots for each device
 show channels 2-4 in comparison to channel 1.  Note that the
 TwinRx results show much smaller variation (as expected since
 there is a shared LO).  Also note that for UBX results, the
 variation is much smaller for the two channels that are housed in
 the same X310 (top right plot).  I suspect that the much larger
 variations shown for the 3rd and 4th channels (relative to
 channel 1) are related to a 10 MHz PLL circuit in each X310. 
 Bottom line is that I see at least +/- 1 degree "wobble" in the
 channel-to-channel phase over time. You'll need to determine if
 this is acceptable for your application.

 Rob


 Inline image 1


 On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users
 <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>>
 wrote:

     On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote:

     Hi everyone!

     I was wondering if anyone knew if it was possible to phase
     align more than 2 X310s (with UBX daughterboard) to form a
     coherent array? I know that 2x2 MIMO is possible using a
     single X310, but I want to be able to sync 4 of them. I
     thought I read somewhere that it was dependent on the
     daughterboard, but I can’t find that thread anywhere.

     Thanks for all the help!

     Yes, use an external 10MHz reference and 1PPS source, like
     the Octoclock, or Octoclock-G, or similar.

     Also, see this App note:

     https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices
     <https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices>

     Description:
     http://www.oceanit.com/sites/default/files/oceanit_sig.png

     	

     *Sarah Tran Leony**|*Electrical Engineer

     828 Fort Street Mall Suite 600
     <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>*|
     <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>*Honolulu,
     HI 96813
     <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>

     Email: *_stran@oceanit.com <mailto:stran@oceanit.com>_*

     Office: 808.531.3017 x139*| *Direct: 808.954.4105
     Fax: 808.531.3177 *| *Mobile: 405.837.2614

     	

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     <https://www.facebook.com/oceanit> *|**Twitter*
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On 11/07/2017 12:32 PM, Rob Kossler wrote: > Yes, y0 and y1 on first motherboard, y2 and y3 on second > motherboard. Unfortunately, I don't know of any options to improve it. > > Rob This is likely, as you point out, due to mutual phase-noise of the reference PLLs between X310s. I'll let the Ettus hardware people comment on whether any improvement is possible. It's a bit surprising that the mutual phase-noise on same-motherboard UBX is as good as it is, since two PLL synthesizers will have some remaining mutual phase-noise even when locked to the same, high-quality, reference. The VCOs are operating independently--they won't be "zigging" and "zagging" at the same time. > > On Tue, Nov 7, 2017 at 11:28 AM, ROBIN TORTORA <tilla@comcast.net > <mailto:tilla@comcast.net>> wrote: > > On the UBX results, Y0 -> Y1, I assume that is in the same > motherboard? > > > Y2 and Y3 on a different motherboard (delta seems to be much > larger, but very very similar across Y2 and Y3 relative to Y0)? > > > So if I wanted to improve on the "error" on channels 3 and 4 or > add more channels, are there any options? > > > Lets assume I have done the easy things like match cable lengths > and use splitters with low phase balance etc. :) > >> On November 6, 2017 at 6:33 PM Rob Kossler via USRP-users >> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> >> wrote: >> >> Sarah, >> I just happen to be in the middle of an evaluation presently of >> the channel-to-channel phase coherence among various 4 chan >> receivers, among them an X310/UBX (pair) and X310/TwinRx. For >> this test, I inject a CW tone (-48 dBm) into a 1:4 power divider >> which then feeds the four receiver channels. I then compute the >> cross correlation (in 1 msec blocks, zero lag) between each of >> channels 2-4 and channel 1 (arbitrarily selected as the reference >> channel). The following figure shows the channel-to-channel >> phase variation over a 2 sec window. The left plots are for the >> four channel X310/TwinRx. The right plots are for the pair of >> X310/UBX (appropriately synced). The 3 plots for each device >> show channels 2-4 in comparison to channel 1. Note that the >> TwinRx results show much smaller variation (as expected since >> there is a shared LO). Also note that for UBX results, the >> variation is much smaller for the two channels that are housed in >> the same X310 (top right plot). I suspect that the much larger >> variations shown for the 3rd and 4th channels (relative to >> channel 1) are related to a 10 MHz PLL circuit in each X310. >> Bottom line is that I see at least +/- 1 degree "wobble" in the >> channel-to-channel phase over time. You'll need to determine if >> this is acceptable for your application. >> >> Rob >> >> >> Inline image 1 >> >> >> On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users >> <usrp-users@lists.ettus.com <mailto:usrp-users@lists.ettus.com>> >> wrote: >> >> On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: >>> >>> Hi everyone! >>> >>> I was wondering if anyone knew if it was possible to phase >>> align more than 2 X310s (with UBX daughterboard) to form a >>> coherent array? I know that 2x2 MIMO is possible using a >>> single X310, but I want to be able to sync 4 of them. I >>> thought I read somewhere that it was dependent on the >>> daughterboard, but I can’t find that thread anywhere. >>> >>> Thanks for all the help! >>> >> Yes, use an external 10MHz reference and 1PPS source, like >> the Octoclock, or Octoclock-G, or similar. >> >> Also, see this App note: >> >> https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices >> <https://kb.ettus.com/Synchronization_and_MIMO_Capability_with_USRP_Devices> >> >>> >>> Description: >>> http://www.oceanit.com/sites/default/files/oceanit_sig.png >>> >>> >>> >>> *Sarah Tran Leony**|*Electrical Engineer >>> >>> 828 Fort Street Mall Suite 600 >>> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>*| >>> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>*Honolulu, >>> HI 96813 >>> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g> >>> >>> Email: *_stran@oceanit.com <mailto:stran@oceanit.com>_* >>> >>> Office: 808.531.3017 x139*| *Direct: 808.954.4105 >>> Fax: 808.531.3177 *| *Mobile: 405.837.2614 >>> >>> >>> >>> *Click *►*Website* <http://www.oceanit.com/> *|**Facebook* >>> <https://www.facebook.com/oceanit> *|**Twitter* >>> <http://twitter.com/oceanit> *|**LinkedIn* >>> <https://www.linkedin.com/company/oceanit> >>> >>> Description: >>> http://www.oceanit.com/sites/default/files/tree_sig.pngPlease consider >>> the environment before printing this message. >>> >>> NOTICE TO RECIPIENT: This message may contain confidential >>> or privileged information and any unauthorized use, >>> disclosure or copying of this message or its contents is >>> prohibited. If you are not the intended recipient, please >>> reply to advise the sender of the error and immediately >>> delete this message and any attachments from your system. >>> >>> >>> >>> _______________________________________________ >>> 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 <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 >> <http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> >> >> >

Marcus, Perhaps the same motherboard results are not as good as my previous figure indicated. Because my processing used a block size of 1 msec, I was likely averaging any oscillations occurring much faster than that. Here is a new plot using a block size of 100 usec. Note that the pk-pk variation is about 0.3 deg and that the signal structure is not very noise-like. This is likely the zig/zag you mentioned. So, not as good as the previous figure, but still not too bad. Rob [image: Inline image 1] On Tue, Nov 7, 2017 at 1:15 PM, Marcus D. Leech <mleech@ripnet.com> wrote: > On 11/07/2017 12:32 PM, Rob Kossler wrote: > > Yes, y0 and y1 on first motherboard, y2 and y3 on second motherboard. > Unfortunately, I don't know of any options to improve it. > > Rob > > This is likely, as you point out, due to mutual phase-noise of the > reference PLLs between X310s. I'll let the Ettus hardware people comment > on whether any improvement is possible. > > It's a bit surprising that the mutual phase-noise on same-motherboard UBX > is as good as it is, since two PLL synthesizers will have some remaining > mutual phase-noise even when locked to the same, high-quality, > reference. The VCOs are operating independently--they won't be "zigging" > and "zagging" at the same time. > > > > On Tue, Nov 7, 2017 at 11:28 AM, ROBIN TORTORA <tilla@comcast.net> wrote: > >> On the UBX results, Y0 -> Y1, I assume that is in the same motherboard? >> >> >> Y2 and Y3 on a different motherboard (delta seems to be much larger, but >> very very similar across Y2 and Y3 relative to Y0)? >> >> >> So if I wanted to improve on the "error" on channels 3 and 4 or add more >> channels, are there any options? >> >> >> Lets assume I have done the easy things like match cable lengths and use >> splitters with low phase balance etc. :) >> >> On November 6, 2017 at 6:33 PM Rob Kossler via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >> Sarah, >> I just happen to be in the middle of an evaluation presently of the >> channel-to-channel phase coherence among various 4 chan receivers, among >> them an X310/UBX (pair) and X310/TwinRx. For this test, I inject a CW tone >> (-48 dBm) into a 1:4 power divider which then feeds the four receiver >> channels. I then compute the cross correlation (in 1 msec blocks, zero lag) >> between each of channels 2-4 and channel 1 (arbitrarily selected as the >> reference channel). The following figure shows the channel-to-channel >> phase variation over a 2 sec window. The left plots are for the four >> channel X310/TwinRx. The right plots are for the pair of X310/UBX >> (appropriately synced). The 3 plots for each device show channels 2-4 in >> comparison to channel 1. Note that the TwinRx results show much smaller >> variation (as expected since there is a shared LO). Also note that for UBX >> results, the variation is much smaller for the two channels that are housed >> in the same X310 (top right plot). I suspect that the much larger >> variations shown for the 3rd and 4th channels (relative to channel 1) are >> related to a 10 MHz PLL circuit in each X310. Bottom line is that I see at >> least +/- 1 degree "wobble" in the channel-to-channel phase over time. >> You'll need to determine if this is acceptable for your application. >> >> Rob >> >> >> [image: Inline image 1] >> >> >> On Mon, Nov 6, 2017 at 5:11 PM, Marcus D. Leech via USRP-users < >> usrp-users@lists.ettus.com> wrote: >> >> On 11/06/2017 04:57 PM, Sarah Tran via USRP-users wrote: >> >> Hi everyone! >> >> >> >> I was wondering if anyone knew if it was possible to phase align more >> than 2 X310s (with UBX daughterboard) to form a coherent array? I know that >> 2x2 MIMO is possible using a single X310, but I want to be able to sync 4 >> of them. I thought I read somewhere that it was dependent on the >> daughterboard, but I can’t find that thread anywhere. >> >> >> >> Thanks for all the help! >> >> Yes, use an external 10MHz reference and 1PPS source, like the Octoclock, >> or Octoclock-G, or similar. >> >> Also, see this App note: >> >> https://kb.ettus.com/Synchronization_and_MIMO_Capability_wit >> h_USRP_Devices >> >> >> >> >> >> >> >> >> >> [image: Description: >> http://www.oceanit.com/sites/default/files/oceanit_sig.png] >> >> *Sarah Tran Leony* *|* Electrical Engineer >> >> 828 Fort Street Mall Suite 600 >> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g> >> *| >> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g>* >> Honolulu, HI 96813 >> <https://maps.google.com/?q=828+Fort+Street+Mall+Suite+600+%C2%A0%7C%C2%A0+Honolulu,+HI+96813&entry=gmail&source=g> >> >> Email: *stran@oceanit.com <stran@oceanit.com>* >> >> Office: 808.531.3017 x139 *| >> <https://maps.google.com/?q=828%0D+Fort+Street+Mall+Suite%0D+600%0D+%C2%A0%7C+%3Chttps://maps.google.com/?q%3D828%2BFort%2BStreet%2BMall%2BSuite%2B600%2B%25C2%25A0%257C%25C2%25A0%2BHonolulu,%2BHI%2B96813%26entry%3Dgmail%26source%3Dg%3E%C2%A0%0D+Honolulu,%0D+HI+96813+%3Chttps://maps.google.com/?q%3D828%2BFort%2BStreet%2BMall%2BSuite%2B600%2B%25C2%25A0%257C%25C2%25A0%2BHonolulu,%2BHI%2B96813%26entry%3Dgmail%26source%3Dg%3E&entry=gmail&source=g> >> *Direct: 808.954.4105 >> Fax: 808.531.3177 *| *Mobile: 405.837.2614 >> >> >> >> *Click *► *Website* <http://www.oceanit.com/> *|* *Facebook* >> <https://www.facebook.com/oceanit> *|* *Twitter* >> <http://twitter.com/oceanit> *|* *LinkedIn* >> <https://www.linkedin.com/company/oceanit> >> >> [image: Description: >> http://www.oceanit.com/sites/default/files/tree_sig.png]Please consider >> the environment before printing this message. >> >> NOTICE TO RECIPIENT: This message may contain confidential or privileged >> information and any unauthorized use, disclosure or copying of this message >> or its contents is prohibited. If you are not the intended recipient, >> please reply to advise the sender of the error and immediately delete this >> message and any attachments from your system. >> >> >> >> >> >> >> _______________________________________________ >> USRP-users mailing listUSRP-users@lists.ettus.comhttp://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 >> >> >> > >