Ultra low frequency VCO
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From: krw on 13 Jul 2010 18:24 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. Is anyone here younger than 20? 40? I know a few aren't yet 60. ;-)
From: Phil Hobbs on 13 Jul 2010 22:41 j wrote: >> Genuine phase noise sidebands have flat tops, so they aren't as >> sensitive to modulation frequency as FM noise. Various authors go to >> various lengths in trying to identify regions where the noise goes as >> 1/f, 1/f**2,.... > > What in the world are you saying? Sounds kind of ignorant to me � but > I�ll reserve judgment until you answer. > > I made a living at designing multiloop uw / rf synthesizers and taking > this statement as fact sure wouldn�t have helped. > > regards Which statement? You don't think that pure phase noise is white? Or that different authors say different things? I plead guilty to ignorance of many things. 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: j on 13 Jul 2010 23:58 On Jul 13, 7:41 pm, Phil Hobbs <pcdhSpamMeSensel...(a)electrooptical.net> wrote: > j wrote: > >> Genuine phase noise sidebands have flat tops, so they aren't as > >> sensitive to modulation frequency as FM noise. Various authors go to > >> various lengths in trying to identify regions where the noise goes as > >> 1/f, 1/f**2,.... > > > What in the world are you saying? Sounds kind of ignorant to me but > > Ill reserve judgment until you answer. > > > I made a living at designing multiloop uw / rf synthesizers and taking > > this statement as fact sure wouldnt have helped. > > > regards > > Which statement? You don't think that pure phase noise is white? Or > that different authors say different things? > > I plead guilty to ignorance of many things. > > 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 nethttp://electrooptical.net Yeah, I suspected you were talking about white noise. Unfortunately for folks that design low noise freq synthesizers white noise isnt the tough spot. We typically live in those 1/f places. The whole process is about shaping that noise profile. Without targeted system specs, one can see why its virtually impossible to select loop components such as a VCOs, amps, etc., for this type of job. Btw, I apologize for the ignorant comment didnt mean to sound so nasty. I regret that.
From: Paul Keinanen on 14 Jul 2010 00:16 On Tue, 13 Jul 2010 08:36:35 -0700, Tim Wescott <tim(a)seemywebsite.com> wrote: >On 07/12/2010 11:42 PM, Geoff C 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. > >No kidding! If he's within 10 degrees one way or another that's >probably plenty good. > >Of far greater concern with PV usage is making sure that putting what is >essentially a negative resistance on the line won't cause instability, >or at least knowing exactly what conditions will lead to instability so >that you may avoid them during installation. > >Particularly if you're going to move from your lab with one or two PV >panels attached to a good solid grid, to some solar farm out in the >boonies where your PV array is the biggest power source for miles. In remote areas, the electricity distribution network is often like a tree (not a ring) and becomes weaker when approaching the leaves of the tree. Connecting one or more 1-3 MW wind turbines at the edges will cause problems. Ideally, it is assumed that the turbine should provide power to the customers at the local branch. However, when operated close to the cut-in wind speed, the power output will vary significantly, causing voltage variations and the lights will flicker at nearby customers in the weak net. With wind turbines at different branches of a weak net, some operated below average, some above average power, power is routed long distances along weak lines through the common distribution point of the original distribution net. The direction of power transfer in the weak lines varies constantly, depending on the local wind variations. In effect, the wind turbines in different branches have a slightly different phase compared to each other and the main power grid. When connecting individual PV or other small scale power sources to a weak net, the control loops must be able to follow much faster phase variations in weak nets with local generation, compared to a strong network.
From: JosephKK on 14 Jul 2010 00:49
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. >>>>> >>>>> Itâs 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 itâs 60 Hz or several GHzâs 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 >>>>> doesnât matter. But Iâd 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. |