how to adjust 10mHz phase to instruments? (fine and coarse) - Page 1
Forum section: electronics / projects

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 08, 2015, 01:07:14 am
content: What stable instrumentation is recommended to adjust 10 MHz atomic clock going to various instrumentation with fine phase resolution (0.001 degree)?I would not mind a coarse adjustment box (i.e. 0-360 degrees 0.1 deg resolution) and then a fine adjustment box (much better with a 1 degree span)preferably some sort of phase distribution box (i.e. 4 to 400 outputs ) .

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 08, 2015, 01:14:41 am
content: I realize that eventually I will need to cut coaxial cable to length to use speed of light as a phase shift adjustment method but I need some sort of crude digital preregulator.

author: Howardlong
author_rank: Super Contributor
timestamp: September 08, 2015, 01:18:50 am
content: What is it you're trying to achieve by adjusting the phase?There are distribution amplifiers to provide multiple coherent outputs, as you may already know, but I don't know of any with individual phase shifting capability.In its simplest form, a variable capacitor will do phase shifting for you.

author: moffy
author_rank: Super Contributor
timestamp: September 08, 2015, 01:28:03 am
content: 0.001 degree at 10MHz is 0.2ps, really?!

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 08, 2015, 01:49:51 am
content: Quote from: moffy on September 08, 2015, 01:28:03 am10ps is is like 0.04 degreeis there something like the AD9500/AD9501 but more stable/finer resolution (the tempco on that shit is pretty terrible!)Is doing this with a FPGA practical or does it introduce too much jitter (compared to say that AD9500 ASIC).i could live with an IC that has 1pS adjustment steps...

author: moffy
author_rank: Super Contributor
timestamp: September 08, 2015, 02:12:26 am
content: I would start with the jitter specification on your clock source. There is no point aiming at much better timing resolution than the basic jitter of your clock source.

author: rs20
author_rank: Super Contributor
timestamp: September 08, 2015, 02:15:14 am
content: Quote from: sarepairman2 on September 08, 2015, 01:49:51 ams = seconds (time)S = siemens (conductivity)Anyway, there was a video on the Signal Path blog that included a phase adjuster, basically a variable-length bit of microstrip in a metal box. Kind of arranged like a trombone. Edit: here it ishttps://youtu.be/6kwamCh1QkE?t=40m30sSECOND EDIT: It just crossed my mind that a 360 degree phase shift at 10 MHz requires a trombone about 10 metres long. So ah, ignore me!

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 08, 2015, 02:20:18 am
content: ooo i renember that video now... ima be the lightspeed dj soon enough with a bunch of sliders lol\at 10MHz I feel like a cookie tin phase delay device might be feasible?

author: sarepairman2
author_rank: Frequent Contributor
timestamp: September 08, 2015, 02:59:06 am
content: Quote from: rs20 on September 08, 2015, 02:15:14 amno, i can use an IC to do the full range then use long micrometers to push some wood/etc to do like a 0.05 degree multi channel trim, this is an excellent idea so long i ovenize the phase delay octal IC phase preregulator circuitinferometer hello

author: LaserSteve
author_rank: Super Contributor
timestamp: September 08, 2015, 05:06:46 pm
content: How many 10 Mhz outputs do you REALLY need?Our usual method in the Ultrafast Laser business is to buy a commercial four channel Digital Delay generator, drive it from the the system master clock, delay ALL the outputs as needed. This way we would have programmable lead or lag as needed. In rare cases we could end up using a simpler box from Allen Avionics which is a programmable analog video delay built to mimic a coax line delay.I just checked Minicircuits and they do not have a stock voltage controlled phase shifter module at 10 Mhz. Although they do have them at lower and higher frequencies. Even if they did, I doubt it would reach your accuracy requirements.I'd take a look at the Highland Technologies Inc, Stanford Research Systems Inc, and Quantum Composers Inc, web sites.Highland Technologies specializes in that sort of low jitter, multiple output timing. John Larkin at Highland makes a lot of custom stuff that does not show up on the web site, so you might wish to speak to him.If you need to roll your own take a look at these two FPGA based designs:A simple, precise, and low jitter delay/gate generatorJ. Kalisz1, A. Poniecki1 and K. Ró?yc1 Rev. Sci. Instrum. 74, 3507 (2003);Accurate and low jitter time-interval generators based on phase shifting method.P. Kwiatkowski1, Z. Jachna1,a), K. Ró?yc1 and J. Kalisz1 Rev. Sci. Instrum. 83, 034701 (2012)And the best one, but it uses a ASIC:Low-jitter wide-range integrated time interval/delay generator based on combination of period counting and capacitor chargingK. Klepacki, M. Paw?owski, and R. Szplet, Review of Scientific Instruments 86, 025111 (2015); doi: 10.1063/1.4908199Usually you can find a few used Digital Delay Generators on Ebay...I'm curious why you would need 400 precise clock stations? Are you working on a kilometer ring accelerator or something similar?I used to deal with this sort of stuff in a former career.If we had to do so something really nasty, like sink the laser mode locking to the master bunching clock of a accelerator, generally they would have a stable house clock distribution at 380 Mhz or 1 Ghz on hard coax to align local edges with. Each station at a ring or Linac would have a clock bench divided down, synced, and preadjusted, for delay. Generally the details of such systems get published, so you might want to look for research papers from that area. If you really needed 400 outputs, that is the way to go.Start with the search term "Clock Distribution" on Google and you'll get lots of hits, including chipsets from companies other then AD.Steve

author: Lukas
author_rank: Frequent Contributor
timestamp: September 08, 2015, 08:30:33 pm
content: Have a look at DDS generators. Some allow fine-tuning the phase.

author: lincoln
author_rank: Regular Contributor
timestamp: September 10, 2015, 09:34:52 pm
content: Quote from: Lukas on September 08, 2015, 08:30:33 pm... but generally have (compared with an crystal OCXO) terrible phase noise. Or at least the methods that I am aware of. There are parts like silicon labs si5348 that has a DCO function and can be used to offset phase.

author: jlmoon
author_rank: Unknown
timestamp: September 10, 2015, 09:52:30 pm
content: Is it me or is the last post simply inappropriate

author: lincoln
author_rank: Regular Contributor
timestamp: September 10, 2015, 09:54:10 pm
content: Quote from: jlmoon on September 10, 2015, 09:52:30 pmMade me laugh....

author: Lukas
author_rank: Frequent Contributor
timestamp: September 10, 2015, 10:49:59 pm
content: Quote from: lincoln on September 10, 2015, 09:34:52 pmIf phase noise is an issue, take a look at fractional-n PLLs. The HMC703 offers a mode that allows for shifting the phase with a resolution of 360deg/2²?. Should be enough. This further increases if you're phase-shifting a multiple of 10MHz and then dividing it .