Hi Dave, thanks very much for the details and for taking the time to
take the data and I'm looking forward to seeing how it turns out.
Best,
Karl
On 8/20/2024 3:17 PM, 'Hawkins, David W (US 334B)' via
casper@lists.berkeley.edu wrote:
Hi Karl,
>> If you had a file of samples from the Wenzel or one of your other
sources you are willing to share, I would like to take a look.
I've been doing some DAC tests this week, but I'll get the ADC setup
in the next week or so and grab some samples.
>> How are you clocking the TI ADC in your tests?
On the custom hardware design we have a reference clock (synth or
Wenzel) feeding the LMX synthesizer which generates 5400MHz, one
output clocks the DAC and the other to the LMK, the LMK divides-by-2
(a space part feature) and then distributes that clock to the ADC and
to dividers that are used to make the REFCLK and CORECLK.
So the two test setups I can grab data for easily will be synth vs
Wenzel. I'll get Rhode&Swartz phase-noise results for the DAC output,
and loop that DAC output into the ADC input (probably through an
analog filter), and look at that data.
I'll use a relatively-prime tone, so that I can exercise as many DAC
and ADC codes as I can.
And I'm sure I'll decide that I did something wrong, and will need to
take more data 😊
Regards,
Dave
-----Original Message-----
From: casper@lists.berkeley.edu <casper@lists.berkeley.edu> On Behalf
Of Karl Warnick
Sent: Tuesday, August 20, 2024 2:10 PM
To: 'Hawkins, David W (US 334B)' via casper@lists.berkeley.edu
<casper@lists.berkeley.edu>
Subject: Re: [EXTERNAL] [casper] Low cost phase noise analysis
Hi Dave, thanks for responding.
I looked into the Wenzel reference just now and found -170 dBc/Hz at
100 kHz for one of their 100-200 MHz products. That's pretty close to
the spec for a 25 MHz low phase noise circuit I bought on ebay for
$100, and just above the thermal noise floor for a clock with a few
dBm or so of power.
If you had a file of samples from the Wenzel or one of your other
sources you are willing to share, I would like to take a look.
My basic question is fairly simple. Are modern samplers low cost with
a good reference clock stable enough to measure phase noise that low
with real samples only and without the need for two channels or cross
correlations? I could answer that question I think with a file of
samples from a decently stable setup.
How are you clocking the TI ADC in your tests?
Best,
Karl
On 8/20/2024 2:49 PM, 'Hawkins, David W (US 334B)' via
casper@lists.berkeley.edu <mailto:casper@lists.berkeley.edu> wrote:
> Hi Karl,
>
>>> Thanks in advance to anyone whose interest is piqued enough to
respond.
> My interest in piqued ...
>
> I'm in the process of measuring phase noise using a Rhode&Swartz on
some EVMs and custom designs:
>
> 1. Texas Instruments DAC39RF10 DAC (I have rev1 and rev2 of their
> space parts) 2. Texas Instruments ADC12DJ3200 ADC (QMLV part) 3.
> LMX2615-SP synthesizer 4. LMK04832-SP clock distribution 5. Wenzel
> low-phase-noise 108MHz and 2700MHz reference (5400MHz and 10800MHz
> also options) 6. Keysight N5183B synthesizer
>
> The DAC and ADC are JESD204C devices. The application is radars
(space-based).
>
> The ADC EVM plugs into the FMC site on a KCU105, so could fill the
DDR on that.
>
> I'm playing with these toys to determine what we don't link. So far
the LMX device is the weakest-link (largest source of phase noise). My
original plan had been to take 108MHz to make 5400MHz for the DAC,
2700MHz for the ADC, and 168.75MHz for the FPGA REFCLK/CORE clock. But
the phase noise of the LMX may change my mind to bring the 5400MHz
directly from the Wenzel. The Wenzel phase noise is nicer as they use
doubler to get to higher frequency rather than a PLL.
>
> So my "toys" might just have the low-phase-noise and
higher-phase-noise that you are looking for to provide your
algorithms. We would have the Rhode&Swartz analyzer for comparison.
>
> Regards,
> Dave
>
>
> Dr David Hawkins
> Technical Group Supervisor
> Radar Science & Engineering Section
> Radar Digital Systems Group (334B)
> Jet Propulsion Laboratory
> 4800 Oak Grove Dr
> Pasadena, CA 91109
> Office: 300-235R
> Phone: 818-354-2252
> Cell: 626-720-7079
> https://radar.jpl.nasa.gov/ <https://radar.jpl.nasa.gov/>
>
>
> -----Original Message-----
> From: casper@lists.berkeley.edu <mailto:casper@lists.berkeley.edu>
<casper@lists.berkeley.edu <mailto:casper@lists.berkeley.edu>> On Behalf
> Of Karl Warnick
> Sent: Tuesday, August 20, 2024 1:38 PM
> To: casper@lists.berkeley.edu <mailto:casper@lists.berkeley.edu>
> Subject: [EXTERNAL] [casper] Low cost phase noise analysis
>
> Hi all,
>
> I've spent some time this summer as part of a radar project digging
into calculating phase noise for highly stable tones. I have
implemented what I think is a decent algorithm. My next steps are to
look for test data sets and tips for the hardware.
>
> Do you have a file of samples of a stable tone? If anyone has a test
data set consisting of samples of a pure tone that they would like to
share as a test data set, I'd like to apply my codes to that and check
the phase noise. Both the tone generator and the ADC sample clock
should be phase stable to the order of a Keysight signal generator, or
ideally better. The data set length should be a reasonable fraction of
a second for ~1 Hz phase noise resolution. The frequency of the tone
and the sample rate are fairly arbitrary as I'm mainly looking to
benchmark the algorithm.
>
> How cheaply can stable samples be acquired? I'm looking for low cost
hardware (a few $100s up to a few $k) that is stable enough to measure
phase noise comparable to a Keysight source or better. Phase noise can
be measured with an expensive phase noise analyzer, but I believe it
should be possible to do this with a low cost digitizer with a
suitably stable sample clock. The sample clock could (or perhaps must)
be external. The sample rate should be around 80-100 Msps or higher
and the platform should be able to store a burst of samples of length
on the order of 1 sec. We have done this using a ZCU 216 and it seems
to work, but that isn't really a low cost board. I've looked into
Picoscope products, which might be ideal, but their support people
don't know anything about the phase noise properties of their samplers.
>
> Thanks in advance to anyone whose interest is piqued enough to respond.
>
> Best,
> Karl
>
> --
> Karl F. Warnick
> Parkinson Engineering Research Professor Department of Electrical and
> Computer Engineering Brigham Young University
> 450 Engineering Building
> Provo, UT 84602
> (801) 422-1732
>
>
>
>
>
--
Karl F. Warnick
Parkinson Engineering Research Professor Department of Electrical and
Computer Engineering Brigham Young University
450 Engineering Building
Provo, UT 84602
(801) 422-1732
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Parkinson Engineering Research Professor
Department of Electrical and Computer Engineering
Brigham Young University
450 Engineering Building
Provo, UT 84602
(801) 422-1732
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