Ultra low frequency VCO
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From: Phil Hobbs on 12 Jul 2010 11:27 Phil Hobbs wrote: > For instance, if you have a 1 MHz resonator with a Q of a million, it > takes a second or so to get its phase to change when you put PM on the > drive waveform. OTOH, if you change the resonant frequency suddenly, > e.g. by putting 100V on a Y5V tank capacitor, the resonant frequency > changes immediately--much faster than 1/Q cycles. Much faster than Q cycles, I mean. (Posted before breakfast in Albuquerque.) > Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Phil Hobbs on 12 Jul 2010 11:30 j wrote: > It�s not that it�s not interesting � but you need to change the topic > to phase noise measurements or something of that nature. Or stable > low freq Osc for example. > > It appears that the OP wanted to discipline to line and use that as a > long term ref.. It�s not clear to me how he came up with the �100 dBc > number without an offset � > > I�m not sure what you mean by �how big an offset� � offset generally > refers to the position of the measurement relative to the carrier. > The closer the offset the more difficult the measurement ... generally > do to the limitation of the measuring equipment. The interesting part > is the solution to those challenges. > > I�m not trying to be a malcontent here � just seems like the > discussion doesn�t have direction. Understood. I agree that the OP's question wasn't that well posed, but there was a bunch of very strongly stated Bad Info here that needed pointing out. I took the OP to be saying "I need a 60 Hz oscillator block that's way, way quieter than I know how to build", and that the rest of us have been making suggestions. Calculating or measuring how good it actually is is his worry. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 12 Jul 2010 11:33 On Mon, 12 Jul 2010 10:40:00 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >Jim Thompson wrote: >> On Fri, 09 Jul 2010 14:08:28 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> whit3rd wrote: >>>> On Jul 8, 12:29 pm, Phil Hobbs >>>> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >>>> >>>>> I don't know that -100 dBc/Hz is that hard at 60 Hz. I bet you could do >>>>> that by running a bog standard multivibrator at 1024*1024*60 Hz and >>>>> dividing down. You'd need a sine shaper, but the phase noise goes down >>>>> by N**2 >>>> Eh? I'd think it's N**0.5 (the multivibrator has cumulative but >>>> random errors). >>> The time jitter of the edges stays the same, but the resulting phase >>> error goes down by a factor of N due to the division. Phase is like >>> amplitude, so you have to square it to get the noise power--hence N**2. >>> >>> Cheers >>> >>> Phil Hobbs >> >> Hey Phil! How come no comment on conservation of charge and energy? >> You have a dog in this show ?:-) Weenie! >> >> ...Jim Thompson > >I'm mainly here to talk about electronics. One-upmanship also tends to >intimidate the newbies, which I really don't want to do. I try not to >dispense Bad Info myself, and try to help other people's >misunderstandings when I can. Otherwise I just read with interest and >learn stuff. > >Whit3rd seems to be talking about the phase correlations rather than the >instantaneous phase noise. Both multivibrators and LC resonators obey >equations with full locality, i.e. neither one has any memory at all. > >For instance, if you have a 1 MHz resonator with a Q of a million, it >takes a second or so to get its phase to change when you put PM on the >drive waveform. OTOH, if you change the resonant frequency suddenly, >e.g. by putting 100V on a Y5V tank capacitor, the resonant frequency >changes immediately--much faster than 1/Q cycles. > >Because of the switching action, multivibrators intermodulate the >switching element's noise at all frequencies, which makes their jitter >much worse; also the effective Q of a multivibrator is less than 1, >which means that there isn't any significant filtering action from the >resonator. (That's frequency-domain way of thinking about what Whit3rd >is talking about in the time domain--the conservation of energy issue is >easier to think about if there's a natural bandwidth limit to the >sqrt(t) behaviour.) The physical origin of the phase modulation doesn't >change the way it varies with division ratio, though. > >Cheers > >Phil Hobbs One interesting and often overlooked part is the coaxial ceramic resonator. It's essentially a shorted transmission line formed in a block or tube of hi-K ceramic, usually by silver or copper plating it. They are usually treated by the RF boys as resonators or inductors, but they really act like time-domain transmission lines. TCs are in the single-digit PPMs and Qs in the hundreds or thousands. Dielectric constants are in the hundreds or thousands, so they are very short for their delay/frequency. Remarkable parts. I use them to make instant-start/instant-stop oscillators in the 600 MHz range. As a VCO, they will have very low phase noise, somewhere between an LC and a quartz crystal. John
From: John Larkin on 12 Jul 2010 11:38 On Mon, 12 Jul 2010 11:27:43 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >Phil Hobbs wrote: > >> For instance, if you have a 1 MHz resonator with a Q of a million, it >> takes a second or so to get its phase to change when you put PM on the >> drive waveform. OTOH, if you change the resonant frequency suddenly, >> e.g. by putting 100V on a Y5V tank capacitor, the resonant frequency >> changes immediately--much faster than 1/Q cycles. > >Much faster than Q cycles, I mean. (Posted before breakfast in >Albuquerque.) >> > >Cheers > >Phil Hobbs Check out La Posada de Albuquerque. Cool old hotel. Or it was, except they may have "upgraded" it. John
From: Phil Hobbs on 12 Jul 2010 11:43
Jim Thompson wrote: > On Mon, 12 Jul 2010 10:40:00 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> Jim Thompson wrote: >>> On Fri, 09 Jul 2010 14:08:28 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>> whit3rd wrote: >>>>> On Jul 8, 12:29 pm, Phil Hobbs >>>>> <pcdhSpamMeSensel...(a)electrooptical.net> wrote: >>>>> >>>>>> I don't know that -100 dBc/Hz is that hard at 60 Hz. I bet you could do >>>>>> that by running a bog standard multivibrator at 1024*1024*60 Hz and >>>>>> dividing down. You'd need a sine shaper, but the phase noise goes down >>>>>> by N**2 >>>>> Eh? I'd think it's N**0.5 (the multivibrator has cumulative but >>>>> random errors). >>>> The time jitter of the edges stays the same, but the resulting phase >>>> error goes down by a factor of N due to the division. Phase is like >>>> amplitude, so you have to square it to get the noise power--hence N**2. >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> Hey Phil! How come no comment on conservation of charge and energy? >>> You have a dog in this show ?:-) Weenie! >>> >>> ...Jim Thompson >> I'm mainly here to talk about electronics. One-upmanship also tends to >> intimidate the newbies, which I really don't want to do. I try not to >> dispense Bad Info myself, and try to help other people's >> misunderstandings when I can. Otherwise I just read with interest and >> learn stuff. > > There's no one-up-man-ship involved. Larkin won't (or can't, because > he doesn't really understand it) show where the extra charge came > from. You (or Win) could put a stop to Larkin's nonsense. Larkin > displays me as a fool, and the newbies don't know any better, so > they'll never ever learn the correct solution unless someone > (politically :) respected steps in. I don't know about that. It isn't that difficult to calculate a circuit with two caps, an inductor, and an elf who opens and closes a switch at the right moments. It does help to know elementary differential equations. I haven't actually followed the original discussion closely enough to know who made the first technical error. The larger error IMO is to keep getting into these tiresome p***ing contests, which I decline to do. If what you want is merely to have the correct solution posted, post it and let's move on to some electronics. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net |