Ultra low frequency VCO
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From: JosephKK on 14 Jul 2010 01:00 On Mon, 12 Jul 2010 23:29:42 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >JosephKK wrote: >> On Mon, 12 Jul 2010 09:39:54 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> JosephKK wrote: >>>> On Fri, 09 Jul 2010 11:56:28 -0400, Phil Hobbs >>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>> >>>>> On 7/9/2010 8:59 AM, JosephKK wrote: >>>>>> On Thu, 08 Jul 2010 15:37:28 -0400, Phil Hobbs >>>>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>>>> >>>>>>> Phil Hobbs 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, so you'd get 100 dB improvement just from that. Alternatively, >>>>>>>> you could make an LC VCO and divide that down. >>>>>>> 120 dB. Can't count today. >>>>>>> >>>>>>> Cheers >>>>>>> >>>>>>> Phil Hobbs >>>>>> Sure, you can mathematically "predict" it, but how do you measure it? >>>>>> Or do you switch to another metric which can be both predicted and >>>>>> measured? >>>>> Let's keep the math bashing to the other thread, okay? >>>>> >>>>> Although it isn't highly relevant to the OP's problem, it wouldn't be >>>>> very difficult to measure the residual FM--use MOSFET buffers to drive >>>>> two divider strings running from independent power supplies, and >>>>> cross-correlate their outputs, exchanging them periodically to get rid >>>>> of the drift in the correlator. For the correlator design, see Hanbury >>>>> Brown and Twiss, circa 1963--and they did it with discrete bipolars. >>>>> >>>>> There are hard measurements, but this isn't one of them. >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> My issue was not so much the direct difficulty of the measurement, there >>>> are several fairly straight forward setups. But with the _time_ it would >>>> take to make the measurement using many of those setups. The elapsed >>>> time seriously aggravates other measurement issues, notably including >>>> calibration. >>> Modulation frequency isn't affected by heterodyning or frequency >>> multiplication and division. If you take a 60 MHz sine wave and FM it >>> at 1 Hz modulation frequency and 1 MHz peak frequency deviation (M=1E6), >>> then divide it by a million, you get a 60-Hz sine wave modulated at 1 >>> Hz with a 1-Hz peak frequency division (M=1). >>> >>> Cheers >>> >>> Phil Hobbs >> >> I am sorry. I think i am misreading your post, are you saying you can >> get a 1 MHz deviation on a 60 Hz carrier? Naw, you must be trying to say >> something else and i misunderstood. > > >You can put a 1 MHz phase modulation on a 60 Hz carrier, but you sure >don't wind up with anything pretty. For instance, you could put the 60 >Hz on a varactor-loaded transmission line, and drive the varactors with >1.000000000 MHz. As long as the varactors were driven really >differentially, you wouldn't get any 1.000000000 MHz on the line. > >That's way outside the quasistatic limit, of course, which is where >we're all used to working. It would be a nasty splattery mess, but >you'd get _something_. > >But that wasn't the point I was trying to make. ;) > >Cheers > >Phil Hobbs I understand your post NOT. Please explain more thoroughly, or point me to texts. I still do not understand the way you are using units for phase modulation. I have trouble understanding phase modulating a 60 Hz carrier with a 1 MHz signal. What is the p-p angle you are achieving? How do you know? Sorry about sounding like a fool, but i cannot find common frame for us to understand each other.
From: JosephKK on 14 Jul 2010 01:18 On Mon, 12 Jul 2010 21:01:50 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >On Mon, 12 Jul 2010 20:47:12 -0700, >"JosephKK"<quiettechblue(a)yahoo.com> wrote: > >>On Mon, 12 Jul 2010 09:58:32 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >> >>>On Mon, 12 Jul 2010 08:33:56 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> 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: >>>>>> >><snip> >>>> >>>>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 >>> >>>I've been "using" them... designing them into GPS LO's since before >>>you were born ;-) >>> >>> ...Jim Thompson >> >>That is really good since GPS itself is not that old. > >I did my first Garmin chip more than 20 years ago. > > ...Jim Thompson Larkin only wishes he were that young. No matter, he posts just like such a brash young punk.
From: JosephKK on 14 Jul 2010 01:41 On Tue, 13 Jul 2010 06:42:03 +0000 (UTC), Geoff C <not(a)mail.com> wrote: > >> >> So I guess that all of the suggestions that have been given will work. >> Or none of them. Or some, if only the OP would tell us the rest of >> his requirement. >> > >The OP seems to be interested in syncing his PV solar system to the grid, >at least thats what I infer from reading some other of his posts. Kind of >makes the 100dBc spec look silly if so. If that is the case, a simple twist on the standard PFC circuit will do it. Though that may not meet all of the safety requirements, which are rather difficult.
From: John Larkin on 14 Jul 2010 09:49 On Tue, 13 Jul 2010 22:18:09 -0700, "JosephKK"<quiettechblue(a)yahoo.com> wrote: >On Mon, 12 Jul 2010 21:01:50 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: > >>On Mon, 12 Jul 2010 20:47:12 -0700, >>"JosephKK"<quiettechblue(a)yahoo.com> wrote: >> >>>On Mon, 12 Jul 2010 09:58:32 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >>> >>>>On Mon, 12 Jul 2010 08:33:56 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> 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: >>>>>>> >>><snip> >>>>> >>>>>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 >>>> >>>>I've been "using" them... designing them into GPS LO's since before >>>>you were born ;-) >>>> >>>> ...Jim Thompson >>> >>>That is really good since GPS itself is not that old. >> >>I did my first Garmin chip more than 20 years ago. >> >> ...Jim Thompson > >Larkin only wishes he were that young. No matter, he posts just like >such a brash young punk. Of course I'd like to be young. Wouldn't you? As far as behaving like a "brash young punk", I plead guilty, with pleasure. I hope to keep designing better and faster, and skiing steeper and faster, for a good long time. Electronics is not something you have to give up designing after the age of 30. I knew people who gave up electronics when transistors replaced tubes, and people who refused to learn how to use programmable logic or microprocessors or whatever. May as well move into a managed-care facility and take up miniature golf. John
From: Phil Hobbs on 14 Jul 2010 10:11
On 7/14/2010 12:49 AM, JosephKK wrote: > On Mon, 12 Jul 2010 23:23:56 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> JosephKK wrote: >>> On Mon, 12 Jul 2010 09:37:07 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>> JosephKK wrote: >>>>> On Fri, 9 Jul 2010 10:22:34 -0700 (PDT), j<jdc1789(a)gmail.com> wrote: >>>>> >>>>>> Resolution of noise vs frequency, (as in bw), is the issue in phase >>>>>> noise measurements. The OP never stated the offset from the carrier >>>>>> nor bandwidth. Or maybe I just missed it. >>>>>> >>>>>> It's not clear to me why JosephKK thinks this would be either a time >>>>>> consuming or difficult measurement to make. Assuming the appropriate >>>>>> measurement system is in hand 100 dBc numbers are easily achievable. >>>>>> Whether it's 60 Hz or several GHz's the global issues are the same in >>>>>> making a phase noise measurement. >>>>>> >>>>>> But having said the above, without the OP responding I guess it really >>>>>> doesn't matter. But I'd like to know more about the application and >>>>>> derive solutions from there. >>>>> >>>>> OK. For a carrier of 60 MHz. Pick an instrument or test setup of your >>>>> choice, state the model[s]. Clearly explain just what is going on in the >>>>> measurement and the time it takes to accumulate sufficient data to make >>>>> the measurement. Explain why it takes that much time to reach a reliable >>>>> measurement of -100 dBc phase noise at that carrier frequency. >>>>> >>>>> Now see how well it scales to one million times lower fundamental >>>>> frequency without a similar scaling in measurement time. >>>> It's the modulation frequency that's relevant, not the carrier >>>> frequency. Measurements get slower when you reduce the bandwidth. >>>> >>>> (You can see why this doesn't work if you imagine running it >>>> backwards--mixing or multiplying up to some very high frequency doesn't >>>> allow you to make a measurement with 1 Hz bandwidth any faster. >>>> >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> Now what is the equivalent bandwidth of -100 dBc for a 60 Hz carrier? >>> Since you said 20 log() basis 60 * 10^-5 is 600 microHz. That would have >>> to take some minutes, and if you wanted a proper 10 to 1 measurement >>> buffer, it takes ten times longer. Call it 10,000 seconds? A few hours. >>> And the reference stability etc., i remarked on is coming into play. >> >> >> You're confused, I'm afraid. -100 dBc phase noise in a given bandwidth >> (say 1 Hz, but it doesn't matter) is 7 microradians RMS. Using a 5V >> swing and a CMOS analogue gate as a phase detector, that's >> >> dV = 7e-6 rad RMS * 5V/(pi rad) = 11 microvolts RMS, >> >> which is trivial to measure in a 1 Hz bandwidth in a few seconds--it's >> 80 dB above the noise of a good op amp, so you just have to wait for the >> filter to settle. >> >> Cheers >> >> Phil Hobbs > > OK. I have your "Making it All Work" and AoE 2nd Ed and more. Where do > i go to get less confused? This phase noise measurement is twisted. If you read the derivation in Section 13.6 and do the math, which isn't difficult--just sums and differences of trig functions--we should be talking the same language. The main point is that we discuss small-amplitude phase noise using the small angle approximation, i.e. sin theta ~= theta, so that it's just like amplitude noise except that it's in phase quadrature with the carrier. That makes it a bog-standard propagation-of-errors calculation: you take all the noise sources, multiply them by the relevant partial derivatives, and compute the RMS sum. If you add white noise, half winds up in the I phase, which looks like amplitude variations, and half in the Q phase, which looks like phase variations. The small angle behaviour makes the statistics and frequency spectrum of the resulting phase and amplitude noise equal to those of the original additive noise. It's quite pretty. When the SNR is below about 20 dB, we have to start being a lot more careful mathematically. 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 |