On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote:> >>>> I start an LC oscillator when I get a trigger, and use it to time out > >>>> delays. The ADC is clocked from an OCXO and observes the waveform of > >>>> the triggered LC oscillator, and I close a loop to lock the LC to the > >>>> XO. Actually, the LC frequency is whatever it wants to be. The math > >>>> gets ugly.> I'm thinking along those same lines. If I can (quickly!) measure the > phase angle between my XO and my triggered oscillator, I can seize the > initial phase offset and close a loop on that. ...> My triggered LC oscillator is great for a couple of microseconds, but > is piling up drift and jitter. It needs to be locked to a good XO > long-term.This makes no sense; if you lock it to the XO with any variant of phase-locking, it's NO LONGER phase-locked to the trigger event, and the measurement is worthless. Just cancel the trigger-caused start phase against an XO-caused start phase, and ignore the absolute frequency of the LC entirely (unless you think it drifts enough in a few milliseconds to matter).
non-pipelined fast ADC
Started by ●August 25, 2020
Reply by ●August 30, 20202020-08-30
Reply by ●August 30, 20202020-08-30
On 2020-08-30 17:08, whit3rd wrote:> On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote: > >>>>>> I start an LC oscillator when I get a trigger, and use it to time out >>>>>> delays. The ADC is clocked from an OCXO and observes the waveform of >>>>>> the triggered LC oscillator, and I close a loop to lock the LC to the >>>>>> XO. Actually, the LC frequency is whatever it wants to be. The math >>>>>> gets ugly. > >> I'm thinking along those same lines. If I can (quickly!) measure the >> phase angle between my XO and my triggered oscillator, I can seize the >> initial phase offset and close a loop on that. ... > >> My triggered LC oscillator is great for a couple of microseconds, but >> is piling up drift and jitter. It needs to be locked to a good XO >> long-term. > > This makes no sense; if you lock it to the XO with any variant of phase-locking, > it's NO LONGER phase-locked to the trigger event, and the measurement is worthless. > Just cancel the trigger-caused start phase against an XO-caused start phase, > and ignore the absolute frequency of the LC entirely (unless you think it drifts > enough in a few milliseconds to matter). >You've never actually used a state-of-the-art digital delay generator, I gather. Good ones have jitter down around 10 ps over fairly long periods. Even the SRS DG535 I bought ~25 years ago had jitter less than 100 ps, and newer ones are much better. The idea that an LC oscillator could hold the necessary phase accuracy for milliseconds is ridiculous. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 30, 20202020-08-30
On 2020-08-25 23:09, Ricketty C wrote:> On Tuesday, August 25, 2020 at 2:34:31 PM UTC-4, John Larkin wrote: >> Does anybody know of one? I'd like to digitize 6 bits or so, really >> fast. Most fast ADCs take 3 or 4 clocks to process the data. Even 4 >> bits might work. >> >> Classic "flash" ADCs were fast, but needed 2^N comparators. > > If you want a really fast 6 bit converter look to see what they were selling 20 years ago. > > I'm actually surprised they don't still make them in 6 bits. I thought they mostly went to the complicated architectures to increase the resolution, but I guess the logic can be run faster with pipelining. There's FAST and there's DAMN FAST. That was actually terms used in a National data book if I remember correctly... for buffers I believe. >The LH0033 and LH0063. I asked Bob Pease why their 1990 databook changed it to "fast and very fast", and he said the edict came right from Charlie Sporck. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 30, 20202020-08-30
On 08/28/20 17:47, Phil Hobbs wrote:> On 2020-08-26 14:47, Chris wrote: >> On 08/26/20 19:40, piglet wrote: >>> On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote: >>>> Am 26.08.20 um 18:29 schrieb Chris: >>>> >>>>> >>>>> The older high end HP spectrum analysers, the 8566 and 8568 did that >>>>> as well. The marketing blurb called it lock and roll, locking the >>>>> LO at start of sweep, then free running it open loop for the rest >>>>> of the sweep. Allowed them to have a stable 10Hz resolution bw and >>>>> 1KHz span at Ghz, in the late 1970's. >>>>> >>>>> I think what I was really saying was, was if the solution gets too >>>>> complex, it maybe the wrong approach :-)... >>>> >>>> IIRC, there was an article in the HP Journal about this. >>>> I think I have it on paper somewhere, but HP Journal >>>> is probably searchable somewhere. >>>> >>>> Cheers, Gerhard >>> >>> This one? >>> <http://hparchive.com/Journals/HPJ-1978-06.pdf> >>> >>> piglet >>> >> >> I think i've seen that.Amazing bit of kit for it's time. HP really >> were at the peak of their game back then with tech prowess few, >> if any could match. Much of it still in use today. >> >> Last catalog price for the 8566, iirc, was 78,000 usd and yet, >> they sold bucketloads of them... > > Back in 1982, when I was working in satcom, we had a reasonably new > Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a > bit before it warmed up. > > Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked. > I had one for awhile at IBM, and about 6 years I bought a used one on > eBay when I needed more top end than my previous 8568B. Its close-in > phase noise is remarkably low on account of its YIG-tuned sweep oscillator. > > Its main drawback is that you can have the RF or microwave band > displayed, but not both at once. Still, for 2 cents on the dollar one > really can't complain too loudly. ;) > > Cheers > > Phil Hobbs >Most of the older HP analysers drifted a lot and needed a warmup period of anything up to an hour before they were fit to use. Both the 8566 and 8568 were a step function improvement, in that they were ready for use almost right away, Both use the same display section and the 10Hz resolution bw option is makes them great for close in pjhase noise checking. Have one of each here, came from an rf / emc lab amd must have been on 24/7. Both display sections had a fuzzy tube, but got on to the John Miles site and restored them back to sharp focus. Don't know how long they will last, but only used occasionally, so not a problem. Still a lot of them in use apparently, probably because they have a spec that's difficult to match even now... Chris
Reply by ●August 30, 20202020-08-30
On 2020-08-30 19:17, Chris wrote:> On 08/28/20 17:47, Phil Hobbs wrote: >> On 2020-08-26 14:47, Chris wrote: >>> On 08/26/20 19:40, piglet wrote: >>>> On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote: >>>>> Am 26.08.20 um 18:29 schrieb Chris: >>>>> >>>>>> >>>>>> The older high end HP spectrum analysers, the 8566 and 8568 did that >>>>>> as well. The marketing blurb called it lock and roll, locking the >>>>>> LO at start of sweep, then free running it open loop for the rest >>>>>> of the sweep. Allowed them to have a stable 10Hz resolution bw and >>>>>> 1KHz span at Ghz, in the late 1970's. >>>>>> >>>>>> I think what I was really saying was, was if the solution gets too >>>>>> complex, it maybe the wrong approach :-)... >>>>> >>>>> IIRC, there was an article in the HP Journal about this. >>>>> I think I have it on paper somewhere, but HP Journal >>>>> is probably searchable somewhere. >>>>> >>>>> Cheers, Gerhard >>>> >>>> This one? >>>> <http://hparchive.com/Journals/HPJ-1978-06.pdf> >>>> >>>> piglet >>>> >>> >>> I think i've seen that.Amazing bit of kit for it's time. HP really >>> were at the peak of their game back then with tech prowess few, >>> if any could match. Much of it still in use today. >>> >>> Last catalog price for the 8566, iirc, was 78,000 usd and yet, >>> they sold bucketloads of them... >> >> Back in 1982, when I was working in satcom, we had a reasonably new >> Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a >> bit before it warmed up. >> >> Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked. >> I had one for awhile at IBM, and about 6 years I bought a used one on >> eBay when I needed more top end than my previous 8568B. Its close-in >> phase noise is remarkably low on account of its YIG-tuned sweep >> oscillator. >> >> Its main drawback is that you can have the RF or microwave band >> displayed, but not both at once. Still, for 2 cents on the dollar one >> really can't complain too loudly. ;) >> >> Cheers >> >> Phil Hobbs >> > > Most of the older HP analysers drifted a lot and needed a warmup period > of anything up to an hour before they were fit to use. Both the 8566 and > 8568 were a step function improvement, in that they were ready for use > almost right away, Both use the same display section and the 10Hz > resolution bw option is makes them great for close in pjhase noise > checking. > > Have one of each here, came from an rf / emc lab amd must have been on > 24/7. Both display sections had a fuzzy tube, but got on to the John > Miles site and restored them back to sharp focus. Don't know how long > they will last, but only used occasionally, so not a problem. Still a > lot of them in use apparently, probably because they have a spec that's > difficult to match even now... > > Chris >And getting harder. The SDR-based analyzers are so cheap that they're taking over the market. Cheers Phil "YIG-tuned forever" Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 30, 20202020-08-30
On Sun, 30 Aug 2020 19:06:41 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2020-08-30 17:08, whit3rd wrote: >> On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote: >> >>>>>>> I start an LC oscillator when I get a trigger, and use it to time out >>>>>>> delays. The ADC is clocked from an OCXO and observes the waveform of >>>>>>> the triggered LC oscillator, and I close a loop to lock the LC to the >>>>>>> XO. Actually, the LC frequency is whatever it wants to be. The math >>>>>>> gets ugly. >> >>> I'm thinking along those same lines. If I can (quickly!) measure the >>> phase angle between my XO and my triggered oscillator, I can seize the >>> initial phase offset and close a loop on that. ... >> >>> My triggered LC oscillator is great for a couple of microseconds, but >>> is piling up drift and jitter. It needs to be locked to a good XO >>> long-term. >> >> This makes no sense; if you lock it to the XO with any variant of phase-locking, >> it's NO LONGER phase-locked to the trigger event, and the measurement is worthless. >> Just cancel the trigger-caused start phase against an XO-caused start phase, >> and ignore the absolute frequency of the LC entirely (unless you think it drifts >> enough in a few milliseconds to matter). >> > >You've never actually used a state-of-the-art digital delay generator, I >gather. Good ones have jitter down around 10 ps over fairly long >periods. Even the SRS DG535 I bought ~25 years ago had jitter less than >100 ps, and newer ones are much better. > >The idea that an LC oscillator could hold the necessary phase accuracy >for milliseconds is ridiculous.I did one OEM delay generator that used an unlocked, triggered coaxial ceramic resonator oscillator. It was better than an open-loop LC, but not good enough.> >Cheers > >Phil HobbsThe SRS boxes use the XO to count out time delays. But in the front-end, they measure the delta-T between the external trigger and the local XO clock, and then subtract that out of the back-end pulses. It works sort of OK, but their boxes are user-interface horrors. The DG645 was designed by a guy that I fired. https://www.dropbox.com/s/t7uo7cnybgk74e4/Top_1.jpg?raw=1 https://www.dropbox.com/s/4fmf86rrpne428m/DG645_Connectors.JPG?raw=1 https://www.dropbox.com/s/szg1rzqrp7ut96e/DG645_7-segment.jpg?raw=1 SRS loves to spell out messages in 7-segment. I always thought it would be fun to write a novel in 7-seg text. The French thing apparently uses SERDES blocks in an FPGA. I think the idea is to just run the digital counter stuff really fast. RMS jitter is clock period divided by the square root of 12, which seems magical to me. We'll have a new DDG soon. -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 30, 20202020-08-30
On Sun, 30 Aug 2020 19:28:23 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 2020-08-30 19:17, Chris wrote: >> On 08/28/20 17:47, Phil Hobbs wrote: >>> On 2020-08-26 14:47, Chris wrote: >>>> On 08/26/20 19:40, piglet wrote: >>>>> On 26/08/2020 5:58 pm, Gerhard Hoffmann wrote: >>>>>> Am 26.08.20 um 18:29 schrieb Chris: >>>>>> >>>>>>> >>>>>>> The older high end HP spectrum analysers, the 8566 and 8568 did that >>>>>>> as well.� The marketing blurb called it lock and roll, locking the >>>>>>> LO at start of sweep, then free running it open loop for the rest >>>>>>> of the sweep. Allowed them to have a stable 10Hz resolution bw and >>>>>>> 1KHz span at Ghz, in the late 1970's. >>>>>>> >>>>>>> I think what I was really saying was, was if the solution gets too >>>>>>> complex, it maybe the wrong approach :-)... >>>>>> >>>>>> IIRC, there was an article in the HP Journal about this. >>>>>> I think I have it on paper somewhere, but HP Journal >>>>>> is probably searchable somewhere. >>>>>> >>>>>> Cheers, Gerhard >>>>> >>>>> This one? >>>>> <http://hparchive.com/Journals/HPJ-1978-06.pdf> >>>>> >>>>> piglet >>>>> >>>> >>>> I think i've seen that.Amazing bit of kit for it's time. HP really >>>> were at the peak of their game back then with tech prowess few, >>>> if any could match. Much of it still in use today. >>>> >>>> Last catalog price for the 8566, iirc, was 78,000 usd and yet, >>>> they sold bucketloads of them... >>> >>> Back in 1982, when I was working in satcom, we had a reasonably new >>> Ailtech 757 (iirc). It was a manually-tuned gizmo that drifted around a >>> bit before it warmed up. >>> >>> Then we got a swoopy new HP 8566A, later upgraded to a B. I was hooked. >>> I had one for awhile at IBM, and about 6 years I bought a used one on >>> eBay when I needed more top end than my previous 8568B. Its close-in >>> phase noise is remarkably low on account of its YIG-tuned sweep >>> oscillator. >>> >>> Its main drawback is that you can have the RF or microwave band >>> displayed, but not both at once. Still, for 2 cents on the dollar one >>> really can't complain too loudly. ;) >>> >>> Cheers >>> >>> Phil Hobbs >>> >> >> Most of the older HP analysers drifted a lot and needed a warmup period >> of anything up to an hour before they were fit to use. Both the 8566 and >> 8568 were a step function improvement, in that they were ready for use >> almost right away, Both use the same display section and the 10Hz >> resolution bw option is makes them great for close in pjhase noise >> checking. >> >> Have one of each here, came from an rf / emc lab amd must have been on >> 24/7. Both display sections had a fuzzy tube, but got on to the John >> Miles site and restored them back to sharp focus. Don't know how long >> they will last, but only used occasionally, so not a problem. Still a >> lot of them in use apparently, probably because they have a spec that's >> difficult to match even now... >> >> Chris >> > >And getting harder. The SDR-based analyzers are so cheap that they're >taking over the market. > >Cheers > >Phil "YIG-tuned forever" HobbsIsn't a YIG frequency determined by the mag field? How can that be controlled to PPB precision? -- John Larkin Highland Technology, Inc Science teaches us to doubt. Claude Bernard
Reply by ●August 30, 20202020-08-30
On 08/31/20 00:06, Phil Hobbs wrote:> On 2020-08-30 17:08, whit3rd wrote: >> On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, >> jla...@highlandsniptechnology.com wrote: >> >>>>>>> I start an LC oscillator when I get a trigger, and use it to time >>>>>>> out >>>>>>> delays. The ADC is clocked from an OCXO and observes the waveform of >>>>>>> the triggered LC oscillator, and I close a loop to lock the LC to >>>>>>> the >>>>>>> XO. Actually, the LC frequency is whatever it wants to be. The math >>>>>>> gets ugly. >> >>> I'm thinking along those same lines. If I can (quickly!) measure the >>> phase angle between my XO and my triggered oscillator, I can seize the >>> initial phase offset and close a loop on that. ... >> >>> My triggered LC oscillator is great for a couple of microseconds, but >>> is piling up drift and jitter. It needs to be locked to a good XO >>> long-term. >> >> This makes no sense; if you lock it to the XO with any variant of >> phase-locking, >> it's NO LONGER phase-locked to the trigger event, and the measurement >> is worthless. >> Just cancel the trigger-caused start phase against an XO-caused start >> phase, >> and ignore the absolute frequency of the LC entirely (unless you think >> it drifts >> enough in a few milliseconds to matter). >> > > You've never actually used a state-of-the-art digital delay generator, I > gather. Good ones have jitter down around 10 ps over fairly long > periods. Even the SRS DG535 I bought ~25 years ago had jitter less than > 100 ps, and newer ones are much better. > > The idea that an LC oscillator could hold the necessary phase accuracy > for milliseconds is ridiculous. > > Cheers > > Phil Hobbs >The od HP5359a time synthesiser of similar vintage, should do that as well... Chris
Reply by ●August 30, 20202020-08-30
On 2020-08-30 19:37, jlarkin@highlandsniptechnology.com wrote:> On Sun, 30 Aug 2020 19:06:41 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2020-08-30 17:08, whit3rd wrote: >>> On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, jla...@highlandsniptechnology.com wrote: >>> >>>>>>>> I start an LC oscillator when I get a trigger, and use it to time out >>>>>>>> delays. The ADC is clocked from an OCXO and observes the waveform of >>>>>>>> the triggered LC oscillator, and I close a loop to lock the LC to the >>>>>>>> XO. Actually, the LC frequency is whatever it wants to be. The math >>>>>>>> gets ugly. >>> >>>> I'm thinking along those same lines. If I can (quickly!) measure the >>>> phase angle between my XO and my triggered oscillator, I can seize the >>>> initial phase offset and close a loop on that. ... >>> >>>> My triggered LC oscillator is great for a couple of microseconds, but >>>> is piling up drift and jitter. It needs to be locked to a good XO >>>> long-term. >>> >>> This makes no sense; if you lock it to the XO with any variant of phase-locking, >>> it's NO LONGER phase-locked to the trigger event, and the measurement is worthless. >>> Just cancel the trigger-caused start phase against an XO-caused start phase, >>> and ignore the absolute frequency of the LC entirely (unless you think it drifts >>> enough in a few milliseconds to matter). >>> >> >> You've never actually used a state-of-the-art digital delay generator, I >> gather. Good ones have jitter down around 10 ps over fairly long >> periods. Even the SRS DG535 I bought ~25 years ago had jitter less than >> 100 ps, and newer ones are much better. >> >> The idea that an LC oscillator could hold the necessary phase accuracy >> for milliseconds is ridiculous. > > I did one OEM delay generator that used an unlocked, triggered coaxial > ceramic resonator oscillator. It was better than an open-loop LC, but > not good enough. > > >> >> Cheers >> >> Phil Hobbs > > The SRS boxes use the XO to count out time delays. But in the > front-end, they measure the delta-T between the external trigger and > the local XO clock, and then subtract that out of the back-end pulses. > It works sort of OK, but their boxes are user-interface horrors. The > DG645 was designed by a guy that I fired. > > https://www.dropbox.com/s/t7uo7cnybgk74e4/Top_1.jpg?raw=1 > > https://www.dropbox.com/s/4fmf86rrpne428m/DG645_Connectors.JPG?raw=1 > > https://www.dropbox.com/s/szg1rzqrp7ut96e/DG645_7-segment.jpg?raw=1 > > SRS loves to spell out messages in 7-segment. I always thought it > would be fun to write a novel in 7-seg text.IT UAS A OARK And 5TOrnn4 nI6HT....> > The French thing apparently uses SERDES blocks in an FPGA. I think the > idea is to just run the digital counter stuff really fast. RMS jitter > is clock period divided by the square root of 12, which seems magical > to me.That's the normal RMS uncertainty of an ideal digitizer.> > We'll have a new DDG soon.Looking forward to seeing it! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●August 30, 20202020-08-30
On 2020-08-30 19:55, Chris wrote:> On 08/31/20 00:06, Phil Hobbs wrote: >> On 2020-08-30 17:08, whit3rd wrote: >>> On Sunday, August 30, 2020 at 9:11:07 AM UTC-7, >>> jla...@highlandsniptechnology.com wrote: >>> >>>>>>>> I start an LC oscillator when I get a trigger, and use it to time >>>>>>>> out >>>>>>>> delays. The ADC is clocked from an OCXO and observes the >>>>>>>> waveform of >>>>>>>> the triggered LC oscillator, and I close a loop to lock the LC to >>>>>>>> the >>>>>>>> XO. Actually, the LC frequency is whatever it wants to be. The math >>>>>>>> gets ugly. >>> >>>> I'm thinking along those same lines. If I can (quickly!) measure the >>>> phase angle between my XO and my triggered oscillator, I can seize the >>>> initial phase offset and close a loop on that. ... >>> >>>> My triggered LC oscillator is great for a couple of microseconds, but >>>> is piling up drift and jitter. It needs to be locked to a good XO >>>> long-term. >>> >>> This makes no sense; if you lock it to the XO with any variant of >>> phase-locking, >>> it's NO LONGER phase-locked to the trigger event, and the measurement >>> is worthless. >>> Just cancel the trigger-caused start phase against an XO-caused start >>> phase, >>> and ignore the absolute frequency of the LC entirely (unless you think >>> it drifts >>> enough in a few milliseconds to matter). >>> >> >> You've never actually used a state-of-the-art digital delay generator, I >> gather. Good ones have jitter down around 10 ps over fairly long >> periods. Even the SRS DG535 I bought ~25 years ago had jitter less than >> 100 ps, and newer ones are much better. >> >> The idea that an LC oscillator could hold the necessary phase accuracy >> for milliseconds is ridiculous. >>> > The od HP5359a time synthesiser of similar vintage, should do that as > well...Seems like it was 100 ps typical vs ~10 ps guaranteed for a modern one, and only over a much shorter delay. Making a really good DDG is a hard problem, for sure. I've never built one myself, but I've happily used several, mostly SRS. In my current incarnation I have a Highland P400, which is my go-to pulse generator for most quickish things. Right now I'm working on a POC for a bathymetric lidar, which will use the P400 and some coax cables to clock a dozen or so fast T/Hs at different delays. Good medicine. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
