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List: usrp-users
Subject: [USRP-users] Re: TwinRX Channel Isolation
From: Wan Liu <wan.liu () ettus ! com>
Date: 2022-10-28 2:53:39
Message-ID: CAOcXSJy+13C+pF8cHG7Fixs2vQbwEwAN45c2h59UyYOwsZHv=Q () mail ! gmail ! com
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Hello Brian,
I set up my HW and SW, but I'm having some trouble reproducing after some
initial playing around with UHD examples and gnuradio. I assume you have
some UHD program that records RX to file and while you repeated make tune
requests to ch 1, is this correct? To make sure we are on the same page,
you provide a sample program that reproduces your steps for tuning and
recording the IQ samples.
You also mentioned " When trying to read the lo_locked sensor continuously,
generating SPI traffic I presume going to the PLLs, I get clean spectrum."
Can you also show in your sample program how to reproduce these steps
Once I can get the same spectrogram as you, I'll also look into the "mute
till lock detect" feature of the ADF5356.
Regards,
Wan
On Wed, Oct 26, 2022 at 4:03 PM Brian Padalino <bpadalino@gmail.com> wrote:
> After a bunch of testing, I ended up with the following solution which
> seems to have fixed the vast majority of the issue. There's still extra
> noise, but not nearly as bad as it was previously so I'd appreciate it if
> Ettus still looked into a more complete solution.
>
> For now, I just enabled the "mute till lock detect" feature of the ADF5356
> and ADF4351 PLLs. I modified gen_adf5356_regs.py and gen_adf4351_regs.py
> to default it to be on, and the ld_cyc_count to be the longest possible.
>
> Brian
>
> On Wed, Oct 26, 2022 at 9:38 AM Brian Padalino <bpadalino@gmail.com>
> wrote:
>
>> Hey Wan,
>>
>> On Tue, Oct 25, 2022 at 10:53 PM Wan Liu <wan.liu@ettus.com> wrote:
>>
>>> Hello Brian,
>>>
>>> Thank you for the additional information.
>>>
>>> Regarding #6, I meant that if you have two TwinRX daughterboards, see
>>> if you get this problem when the fixed channel is on one daughterboard, and
>>> the tuned channel is on the other.
>>>
>>
>> Ah, I see. Unfortunately my setup is a mixed USB/TwinRX setup so maybe
>> it isn't exactly testing what you're asking for, but I did use the subdev
>> spec to target the UBX RX2 for hopping around, and the TwinRX Channel 0 was
>> fixed. In this case, the fixed spectrum stayed nice and clean the whole
>> time.
>>
>>
>>>
>>> Regarding screenshots, are you referring to any particular frequency and
>>> time region, or is everything above the noise floor associated with the
>>> tuning? In other words, is the clean spectrum where there is nothing above
>>> the noise floor in both time and frequency plots?
>>>
>>
>> The captures were taken with terminated RF inputs. Channel 0 of the
>> TwinRX was fixed at some frequency (I believe 400 MHz) and Channel 1 was
>> hopping around. The recording was observing Channel 0 - the fixed
>> frequency channel. When no hopping happens, there is clean spectrum with
>> just a noise floor which is what I expected to see. When hopping is
>> happening, every so often we will see these sweeping signals show up. They
>> last around 10 ms or so and then the spectrum is back to being clean.
>>
>>
>>>
>>> Also can you explain what you mean by "shows some analog PLL-style
>>> locking for around 10 ms of time, then goes away"? Are you referring to the
>>> burst from 3 ms to 13 ms, or something specifically at 10 ms?
>>>
>>
>> I meant the phenomenon that starts at around 3 ms and lasts until around
>> 13 ms. It looks like an analog PLL settling to me. Here is a zoomed in
>> version:
>>
>>
>> https://drive.google.com/file/d/1NDax78i3UQh7X_R4g8SHBkBLibI1ICQZ/view?usp=sharing
>>
>>
>>>
>>> Lastly, what are your spectrogram parameters to generate the waterfall?
>>>
>>
>> I am using an FFT size of 2048 with a blackmanharris window of the same
>> size, and overlapping by 1024. My MATLAB command is:
>>
>> spectrogram(slice, blackmanharris(2048), 1024, 2048, 50e6, 'centered');
>>
>>
>>>
>>> I'll reach out again after I attempt to reproduce.
>>>
>>
>> Sounds good. Let me know if you need any other data or clarifications on
>> what I am seeing.
>>
>> Thanks,
>> Brian
>>
>>>
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<div dir="ltr"><div><div><div><div><div>Hello Brian,<br><br></div>I set up my HW and \
SW, but I'm having some trouble reproducing after some initial playing around \
with UHD examples and gnuradio. I assume you have some UHD program that records RX to \
file and while you repeated make tune requests to ch 1, is this correct? To make sure \
we are on the same page, you provide a sample program that reproduces your steps for \
tuning and recording the IQ samples. <br><br></div>You also mentioned " When \
trying to read the lo_locked sensor continuously, generating SPI traffic I presume \
going to the PLLs, I get clean spectrum." Can you also show in your sample \
program how to reproduce these steps<br><br></div>Once I can get the same spectrogram \
as you, I'll also look into the "mute till lock detect" feature of the \
ADF5356.<br><br></div>Regards,<br><br></div>Wan<br></div><br><div \
class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Oct 26, 2022 at 4:03 PM \
Brian Padalino <<a href="mailto:bpadalino@gmail.com">bpadalino@gmail.com</a>> \
wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr">After a \
bunch of testing, I ended up with the following solution which seems to have fixed \
the vast majority of the issue. There's still extra noise, but not nearly as \
bad as it was previously so I'd appreciate it if Ettus still looked into a more \
complete solution.<div><br></div><div>For now, I just enabled the "mute till \
lock detect" feature of the ADF5356 and ADF4351 PLLs. I modified \
gen_adf5356_regs.py and gen_adf4351_regs.py to default it to be on, and the \
ld_cyc_count to be the longest \
possible.</div><div><br></div><div>Brian</div></div><br><div class="gmail_quote"><div \
dir="ltr" class="gmail_attr">On Wed, Oct 26, 2022 at 9:38 AM Brian Padalino <<a \
href="mailto:bpadalino@gmail.com" target="_blank">bpadalino@gmail.com</a>> \
wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div \
dir="ltr">Hey Wan,</div><br><div class="gmail_quote"><div dir="ltr" \
class="gmail_attr">On Tue, Oct 25, 2022 at 10:53 PM Wan Liu <<a \
href="mailto:wan.liu@ettus.com" target="_blank">wan.liu@ettus.com</a>> \
wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px \
0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div \
dir="ltr"><div><div><div>Hello Brian,<br><br></div>Thank you for the additional \
information. <br><br></div>Regarding #6, I meant that if you have two TwinRX \
daughterboards, see if you get this problem when the fixed channel is on one \
daughterboard, and the tuned channel is on the \
other.</div></div></blockquote><div><br></div><div>Ah, I see. Unfortunately my \
setup is a mixed USB/TwinRX setup so maybe it isn't exactly testing what \
you're asking for, but I did use the subdev spec to target the UBX RX2 for \
hopping around, and the TwinRX Channel 0 was fixed. In this case, the fixed \
spectrum stayed nice and clean the whole time.</div><div> </div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div>Regarding \
screenshots, are you referring to any particular frequency and time region, or is \
everything above the noise floor associated with the tuning? In other words, is the \
clean spectrum where there is nothing above the noise floor in both time and \
frequency plots?<br></div></blockquote><div><br></div><div>The captures were taken \
with terminated RF inputs. Channel 0 of the TwinRX was fixed at some frequency (I \
believe 400 MHz) and Channel 1 was hopping around. The recording was observing \
Channel 0 - the fixed frequency channel. When no hopping happens, there is clean \
spectrum with just a noise floor which is what I expected to see. When hopping is \
happening, every so often we will see these sweeping signals show up. They last \
around 10 ms or so and then the spectrum is back to being clean.</div><div> \
</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px \
solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Also can \
you explain what you mean by "shows some analog PLL-style locking for around 10 \
ms of time, then goes away"? Are you referring to the burst from 3 ms to 13 ms, \
or something specifically at 10 ms?<br></div></div></blockquote><div><br></div><div>I \
meant the phenomenon that starts at around 3 ms and lasts until around 13 ms. It \
looks like an analog PLL settling to me. Here is a zoomed in \
version:</div><div><br></div><div> <a \
href="https://drive.google.com/file/d/1NDax78i3UQh7X_R4g8SHBkBLibI1ICQZ/view?usp=sharing" \
target="_blank">https://drive.google.com/file/d/1NDax78i3UQh7X_R4g8SHBkBLibI1ICQZ/view?usp=sharing</a></div><div> \
</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px \
solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>Lastly, \
what are your spectrogram parameters to generate the \
waterfall?<br></div></div></blockquote><div><br></div><div>I am using an FFT size of \
2048 with a blackmanharris window of the same size, and overlapping by 1024. My \
MATLAB command is:</div><div><br></div><div> spectrogram(slice, \
blackmanharris(2048), 1024, 2048, 50e6, 'centered');</div><div> \
</div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px \
solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div><br></div><div>I'll \
reach out again after I attempt to \
reproduce.<br></div></div></blockquote><div><br></div><div>Sounds good. Let me know \
if you need any other data or clarifications on what I am \
seeing.</div><div><br></div><div>Thanks,</div><div>Brian</div><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"><div class="gmail_quote"><blockquote \
class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid \
rgb(204,204,204);padding-left:1ex"> </blockquote></div>
</blockquote></div></div>
</blockquote></div>
</blockquote></div>
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