Re: [USRP-users] Phase drift issue of N310

[Marcus D. Leech via USRP-users]

On 03/21/2019 07:08 AM, Damon wrote:

Hi Marcus,

Thank you for your reply.

I compared the USRP configuration of your grc file with that of mine. 
I found that the key to solve this issue is set_time_next_pps or 
set_time_unknow_pps should be called.


I don't know why   those two functions have an effect on phase error. 
I haven't found any special description of these two functions in the 
N310 manual.


Best regards,

Damon
They'll have an effect on initial phase error, because each half of the 
N310 has its own timekeeper.  If those aren't brought into alignment, then
  the sample streams will be unaligned.  But that should have no effect 
on ongoing phase drift--ONLY on initial phase error.





On 2019/3/21 上午1:07, Marcus D. Leech wrote:

On 03/20/2019 12:55 PM, Damon wrote:

Hi Marcus,

Thanks for your reply.

Yes, it happen with any other frequency changes, not only 460.01M 
and 469.03Mhz.


I'm building a 4-channel coherent receiving system with n310. It 
needs to compensate the phase errors of multiple receiving channels. 
So I need to measure the phase errors first and then compensate 
them. But in the range of 100MHz bandwidth (from center_freq-50MHz 
to  center_freq+50MHz), the phase difference of two receiving 
channels of different dboards varies too much with frequency, so 
it's very difficult to compensate the phase errors. As a contrast, 
the phase errors of the two receiving channels of X310 with ubx vary 
very samll with frequency, so it is easy to compensate the phase 
difference.


Looking forward to your test results

Best regards,

Damon

I used the attached script.

Now, I'm only looking at +/- 2MHz, rather than your 100Mhz bandwidth.

I found that the phase noise and offset did not change noticably 
tuning across the entire 4Mhz band.  I don't have a machine fast 
enough here to
  sweep my TX across 100Mhz, but with the N310 RX at a fixed tuning, 
and sweeping the TX (in this case, a Marconi transceiver test set), I 
did not see
  any significant phase shift or change in mutual phase noise as the 
TX swept across the 4MHz band.





On 2019/3/20 上午10:40, Marcus D. Leech wrote:

On 03/19/2019 09:12 PM, Damon wrote:

Hi Marcus,

The phase  responses of two channels of different dboards 
(ubx-160) in  a X310  are very consistent. When the frequency of 
transmitting signal changes from 460.01MHz to 460.03Mhz, the phase 
difference between two RX channels of different dboards in X310 
remains unchanged. But for the phase difference between two RX 
channels of different dboards of N310,  there are dozens or 
hundreds degree of changes.


Can you try to reproduce the test and help me to figure out how to 
solve it?
I'm not sure if it's a hardware bug, a driver bug or USRP setup 
problem.
I cannot imagine a hardware or driver bug that could produce this 
behavior.  It would mean that the receiver was somehow changing LO

  frequency when the TX frequency changed.

Does this happen with *other* frequency changes, or just 
460.01<--->460.03.  I wonder if you have an interfering signal that 
is being
  "uncovered" by TX frequency change, and you're simply measuring 
that interfering signal?


The only other thing that occurs to me is filtering that is 
extremely non-linear phase.  But that would create such a mess that 
most applications

  would likely not work--clearly they do.

I can try to reproduce in my lab tomorrow, but, like the last tests 
I did, I very much expect to not be able to reproduce.





Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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 

Re: [USRP-users] Phase drift issue of N310

[Damon via USRP-users]

Hi Marcus,

Thank you for your reply.

I compared the USRP configuration of your grc file with that of mine. I 
found that the key to solve this issue is set_time_next_pps or 
set_time_unknow_pps should be called.


I don't know why   those two functions have an effect on phase error. I 
haven't found any special description of these two functions in the N310 
manual.


Best regards,

Damon

On 2019/3/21 上午1:07, Marcus D. Leech wrote:

On 03/20/2019 12:55 PM, Damon wrote:

Hi Marcus,

Thanks for your reply.

Yes, it happen with any other frequency changes, not only 460.01M and 
469.03Mhz.


I'm building a 4-channel coherent receiving system with n310. It 
needs to compensate the phase errors of multiple receiving channels. 
So I need to measure the phase errors first and then compensate them. 
But in the range of 100MHz bandwidth (from center_freq-50MHz to  
center_freq+50MHz), the phase difference of two receiving channels of 
different dboards varies too much with frequency, so it's very 
difficult to compensate the phase errors. As a contrast, the phase 
errors of the two receiving channels of X310 with ubx vary very samll 
with frequency, so it is easy to compensate the phase difference.


Looking forward to your test results

Best regards,

Damon

I used the attached script.

Now, I'm only looking at +/- 2MHz, rather than your 100Mhz bandwidth.

I found that the phase noise and offset did not change noticably 
tuning across the entire 4Mhz band.  I don't have a machine fast 
enough here to
  sweep my TX across 100Mhz, but with the N310 RX at a fixed tuning, 
and sweeping the TX (in this case, a Marconi transceiver test set), I 
did not see
  any significant phase shift or change in mutual phase noise as the 
TX swept across the 4MHz band.





On 2019/3/20 上午10:40, Marcus D. Leech wrote:

On 03/19/2019 09:12 PM, Damon wrote:

Hi Marcus,

The phase  responses of two channels of different dboards (ubx-160) 
in  a X310  are very consistent. When the frequency of transmitting 
signal changes from 460.01MHz to 460.03Mhz, the phase difference 
between two RX channels of different dboards in X310 remains 
unchanged. But for the phase difference between two RX channels of 
different dboards of N310,  there are dozens or hundreds degree of 
changes.


Can you try to reproduce the test and help me to figure out how to 
solve it?
I'm not sure if it's a hardware bug, a driver bug or USRP setup 
problem.
I cannot imagine a hardware or driver bug that could produce this 
behavior.  It would mean that the receiver was somehow changing LO

  frequency when the TX frequency changed.

Does this happen with *other* frequency changes, or just 
460.01<--->460.03.  I wonder if you have an interfering signal that 
is being
  "uncovered" by TX frequency change, and you're simply measuring 
that interfering signal?


The only other thing that occurs to me is filtering that is 
extremely non-linear phase.  But that would create such a mess that 
most applications

  would likely not work--clearly they do.

I can try to reproduce in my lab tomorrow, but, like the last tests 
I did, I very much expect to not be able to reproduce.





Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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 

Re: [USRP-users] Phase drift issue of N310

[Marcus D. Leech via USRP-users]

On 03/20/2019 12:55 PM, Damon wrote:

Hi Marcus,

Thanks for your reply.

Yes, it happen with any other frequency changes, not only 460.01M and 
469.03Mhz.


I'm building a 4-channel coherent receiving system with n310. It needs 
to compensate the phase errors of multiple receiving channels. So I 
need to measure the phase errors first and then compensate them. But 
in the range of 100MHz bandwidth (from center_freq-50MHz to  
center_freq+50MHz), the phase difference of two receiving channels of 
different dboards varies too much with frequency, so it's very 
difficult to compensate the phase errors. As a contrast, the phase 
errors of the two receiving channels of X310 with ubx vary very samll 
with frequency, so it is easy to compensate the phase difference.


Looking forward to your test results

Best regards,

Damon

I used the attached script.

Now, I'm only looking at +/- 2MHz, rather than your 100Mhz bandwidth.

I found that the phase noise and offset did not change noticably tuning 
across the entire 4Mhz band.  I don't have a machine fast enough here to
  sweep my TX across 100Mhz, but with the N310 RX at a fixed tuning, 
and sweeping the TX (in this case, a Marconi transceiver test set), I 
did not see
  any significant phase shift or change in mutual phase noise as the TX 
swept across the 4MHz band.





On 2019/3/20 上午10:40, Marcus D. Leech wrote:

On 03/19/2019 09:12 PM, Damon wrote:

Hi Marcus,

The phase  responses of two channels of different dboards (ubx-160) 
in  a X310  are very consistent. When the frequency of transmitting 
signal changes from 460.01MHz to 460.03Mhz, the phase difference 
between two RX channels of different dboards in X310 remains 
unchanged. But for the phase difference between two RX channels of 
different dboards of N310,  there are dozens or hundreds degree of 
changes.


Can you try to reproduce the test and help me to figure out how to 
solve it?
I'm not sure if it's a hardware bug, a driver bug or USRP setup 
problem.
I cannot imagine a hardware or driver bug that could produce this 
behavior.  It would mean that the receiver was somehow changing LO

  frequency when the TX frequency changed.

Does this happen with *other* frequency changes, or just 
460.01<--->460.03.  I wonder if you have an interfering signal that 
is being
  "uncovered" by TX frequency change, and you're simply measuring 
that interfering signal?


The only other thing that occurs to me is filtering that is extremely 
non-linear phase.  But that would create such a mess that most 
applications

  would likely not work--clearly they do.

I can try to reproduce in my lab tomorrow, but, like the last tests I 
did, I very much expect to not be able to reproduce.





Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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 

Re: [USRP-users] Phase drift issue of N310

[Damon via USRP-users]

Hi Marcus,

Thanks for your reply.

Yes, it happen with any other frequency changes, not only 460.01M and 
469.03Mhz.


I'm building a 4-channel coherent receiving system with n310. It needs 
to compensate the phase errors of multiple receiving channels. So I need 
to measure the phase errors first and then compensate them. But in the 
range of 100MHz bandwidth (from center_freq-50MHz to  
center_freq+50MHz), the phase difference of two receiving channels of 
different dboards varies too much with frequency, so it's very difficult 
to compensate the phase errors. As a contrast, the phase errors of the 
two receiving channels of X310 with ubx vary very samll with frequency, 
so it is easy to compensate the phase difference.


Looking forward to your test results

Best regards,

Damon

On 2019/3/20 上午10:40, Marcus D. Leech wrote:

On 03/19/2019 09:12 PM, Damon wrote:

Hi Marcus,

The phase  responses of two channels of different dboards (ubx-160) 
in  a X310  are very consistent. When the frequency of transmitting 
signal changes from 460.01MHz to 460.03Mhz, the phase difference 
between two RX channels of different dboards in X310 remains 
unchanged. But for the phase difference between two RX channels of 
different dboards of  N310,  there are dozens or hundreds degree of 
changes.


Can you try to reproduce the test and help me to figure out how to 
solve it?

I'm not sure if it's a hardware bug, a driver bug or USRP setup problem.
I cannot imagine a hardware or driver bug that could produce this 
behavior.  It would mean that the receiver was somehow changing LO

  frequency when the TX frequency changed.

Does this happen with *other* frequency changes, or just 
460.01<--->460.03.  I wonder if you have an interfering signal that is 
being
  "uncovered" by TX frequency change, and you're simply measuring that 
interfering signal?


The only other thing that occurs to me is filtering that is extremely 
non-linear phase.  But that would create such a mess that most 
applications

  would likely not work--clearly they do.

I can try to reproduce in my lab tomorrow, but, like the last tests I 
did, I very much expect to not be able to reproduce.





Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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 

Re: [USRP-users] Phase drift issue of N310

[Marcus D. Leech via USRP-users]

On 03/19/2019 09:12 PM, Damon wrote:

Hi Marcus,

The phase  responses of two channels of different dboards (ubx-160) 
in  a X310  are very consistent. When the frequency of transmitting 
signal changes from 460.01MHz to 460.03Mhz, the phase difference 
between two RX channels of different dboards  in X310 remains 
unchanged. But for the phase difference between two RX channels of 
different dboards of  N310,  there are dozens or hundreds degree of 
changes.


Can you try to reproduce the test and help me to figure out how to 
solve it?

I'm not sure if it's a hardware bug, a driver bug or USRP setup problem.
I cannot imagine a hardware or driver bug that could produce this 
behavior.  It would mean that the receiver was somehow changing LO

  frequency when the TX frequency changed.

Does this happen with *other* frequency changes, or just 
460.01<--->460.03.  I wonder if you have an interfering signal that is being
  "uncovered" by TX frequency change, and you're simply measuring that 
interfering signal?


The only other thing that occurs to me is filtering that is extremely 
non-linear phase.  But that would create such a mess that most applications

  would likely not work--clearly they do.

I can try to reproduce in my lab tomorrow, but, like the last tests I 
did, I very much expect to not be able to reproduce.





Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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

[Damon via USRP-users]

Hi Marcus,

The phase  responses of two channels of different dboards (ubx-160) in  
a X310  are very consistent. When the frequency of transmitting signal 
changes from 460.01MHz to 460.03Mhz, the phase difference between two RX 
channels of different dboards  in X310 remains unchanged. But for the 
phase difference between two RX channels of different dboards of  N310,  
there are dozens or hundreds degree of changes.


Can you try to reproduce the test and help me to figure out how to solve it?
I'm not sure if it's a hardware bug, a driver bug or USRP setup problem.

Best regards,
Damon
On 2019/3/19 上午6:10, Marcus D. Leech wrote:

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

[Marcus D. Leech via USRP-users]

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

[Tillson, Bob (US) via USRP-users]

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] Phase drift issue of N310

[Marcus D. Leech via USRP-users]

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

[Marcus D. Leech via USRP-users]

On 03/14/2019 05:07 PM, Ali Dormiani via USRP-users wrote:

Hello all,

Sorry for spreading misinformation. I frequently conflate clock and LO 
incorrectly. Additionally the results I posted are for an array of 
multiple N310's which definitely have different clocks.


I was taught in class that carrier frequency offset happens when an 
access point (AP) and client have imperfect LO's. (EX. wifi router at 
2.41 GHz and laptop at 2.39 Ghz).


Looking at the block diagram, could separate LO's for each AD9361 be 
the source of this phase behavior?


Independent N310s that aren't sharing a reference clock cannot be relied 
upon to have consistent phase and frequency.  This is normal and
  expected.  No two oscillators will operate at precisely the same 
frequency.  The more $$$ you spent on an oscillator, the higher the quality,

  with a non-linear $$$ vs quality curve.

But expecting two independent radios to be on exactly the same frequency 
and phase without an external, common, reference, is not

  realistic at all.








On Thu, Mar 14, 2019 at 1:39 PM Damon via USRP-users 
mailto:usrp-users@lists.ettus.com>> wrote:


Hi Marcus,

The UHD Version is v3.14.0.0-rc1.

Best regards,

Damon

>> 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



___
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 drift issue of N310

[Ali Dormiani via USRP-users]

Hello all,

Sorry for spreading misinformation. I frequently conflate clock and LO
incorrectly. Additionally the results I posted are for an array of multiple
N310's which definitely have different clocks.

I was taught in class that carrier frequency offset happens when an access
point (AP) and client have imperfect LO's. (EX. wifi router at 2.41 GHz and
laptop at 2.39 Ghz).

Looking at the block diagram, could separate LO's for each AD9361 be the
source of this phase behavior?






On Thu, Mar 14, 2019 at 1:39 PM Damon via USRP-users <
usrp-users@lists.ettus.com> wrote:

> Hi Marcus,
>
> The UHD Version is v3.14.0.0-rc1.
>
> Best regards,
>
> Damon
>
> >> 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
>
___
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

[Damon via USRP-users]

Hi Marcus,

The UHD Version is v3.14.0.0-rc1.

Best regards,

Damon


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

[Marcus D. Leech via USRP-users]

On 03/14/2019 03:56 AM, Piotr Krysik via USRP-users wrote:

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

[Piotr Krysik via USRP-users]

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

W dniu 13.03.2019 o 19:59, Ali Dormiani via USRP-users pisze:
> Hello,
>
> You sort of said the answer yourself:
>
> "two dboards are using independent reference clocks"
>
> RX0 and RX1 use the same LO while RX2 and RX3 use a different LO.
>
> I like to think of each N310 as two radios in the same box (when it
> comes to phase issues). Additionally, I think UHD/GNUradio start up RF
> components at run-time so all calibration needs to be preformed each
> time you run a flow-graph or C file?
>
> There are signal processing ways to mitigate this. Consider looking
> into ESPRIT or array shape calibration research.
>
> The hardware fix to this problem is feeding an external LO into each
> N310 dboard.
>
> Attached are some old results from our lab with an 8 TX 24 RX system
> set up indoors (all N310s). You can see that our DOA estimate in
> ESPRIT drifts badly (10 degrees or so) over about a second of data.
>
> The point I'm trying to make is, depending on your application, you
> can avoid buying external LO's, references, ect with some math effort.
>
> However, if you are looking for hardware I suggest Ettus Octoclocks
> for splitting and the following frequency synthesizer:
>
> https://www.valonrf.com/frequency-synthesizer-4400mhz.html
>
> Good luck with your endeavors,
>
> Ali
>
> On Wed, Mar 13, 2019 at 5:52 AM guowang qiu via USRP-users
> mailto:usrp-users@lists.ettus.com>> wrote:
>
> Hi all,
>
> There are two daughter boards in N310, the phase difference
> between channels of different dboards will drift rapidly.
>
> In my test, a B200 transmits single tone continuous wave to a
> 1-to-2 splitter, and the outputs of splitter are connected to
> input ports of RF0 and RF2 of N310.
>
> During the single program running, the signals received by the two
> channels should keep the phase difference approximately stable.
> But I observed that the phase drift of the two channels was very
> fast. Within a time span of 20 seconds, the phase difference
> varied by tens of degrees. Sense that two dboards are using
> independent reference clocks, not the same reference clock from
> mboard. By contrast, the phase difference between the two channels
> of x310 with two ubx is stable.
>
> Does anyone know how to explain this issue?
>
> Best regards,
>
> Damon
>
> ___
> 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

[USRP-users] Phase drift issue of N310

[guowang qiu via USRP-users]

Hi all,

There are two daughter boards in N310, the phase difference between
channels of different dboards will drift rapidly.

In my test, a B200 transmits single tone continuous wave to a 1-to-2
splitter, and the outputs of splitter are connected to input ports of RF0
and RF2 of N310.

During the single program running, the signals received by the two channels
should keep the phase difference approximately stable. But I observed that
the phase drift of the two channels was very fast. Within a time span of 20
seconds, the phase difference varied by tens of degrees. Sense that two
dboards are using independent reference clocks, not the same reference
clock from mboard. By contrast, the phase difference between the two
channels of x310 with two ubx is stable.

Does anyone know how to explain this issue?

Best regards,

Damon
___
USRP-users mailing list
USRP-users@lists.ettus.com
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com