On Monday, November 9, 2015 at 1:59:55 PM UTC-5, Tim Williams wrote:> "Phil Hobbs" wrote in message > news:5b517d7f-dd73-4995-807d-400579d14441@googlegroups.com... > >It should be possible to do it with a magamp too--it's a degenerate > >parametric oscillator. > > > > > Does that mean a magamp oscillator would be expected to produce > frequencies of Fclk/N? Or, perhaps, *M/N for modest values thereof? > > I know very little about parametric amps... All the explanations are > crap, which usually suggests that it's either a stupendously complex > subject, or a preposterously simple one (which is merely being presented > in a confusing manner as a barrier to entry, as many otherwise-simple > academic subjects tend to do). > > Tim > > -- > Seven Transistor Labs, LLC > Electrical Engineering Consultation and Contract Design > Website: http://seventransistorlabs.comHi Tim, Re: parametric amps/ oscillators, I think there is a nice discussion of this in AB. Pippard's "Physics of Vibration, Vol 1." (Wow searching on line I can get both volumes for a few dollars. I haven't read vol II. ) My copy is at home and it's been a while since I've read it. So perhaps I'm mis-remembering. George H. I'm at work and not at home where the text is, but
Magamp oscillator
Started by ●November 3, 2015
Reply by ●November 11, 20152015-11-11
Reply by ●November 11, 20152015-11-11
Phil Hobbs <pcdhobbs@gmail.com> wrote:> Helical and coaxial resonators can easily hit Qs of 600. > > Cheers > > Phil Hobbs >Yes, John has mentioned that before. Doesn't do any good. You can change the series resistance in the ASC file I posted to give a Q of 600. Increase the time to 5us. The oscillations peter out in about 2us. The F/2 signal is merely an artifact of the startup transient. The circuit does not generate a continuous F/2 signal. I am doing further studies on the MV2201 varactor ESR. The datasheet says the series resistance (Rs) is 5.41 ohms. A simple series resonant circuit in LTspice shows the ESR is abot 1.01 ohms at 0.25V bias. So there appears to be a discrepancy between the datasheet and the SPICE model.
Reply by ●November 11, 20152015-11-11
legg <legg@nospam.magma.ca> wrote:> Why bother using a varicap? It's spice, after all.Same problem. Add some realistic ESR and stray capacity and the F/2 signal disappears.
Reply by ●November 11, 20152015-11-11
On Wed, 11 Nov 2015 17:33:17 GMT, Bruce S <nope@lst.com> wrote:>legg <legg@nospam.magma.ca> wrote: > >> Why bother using a varicap? It's spice, after all. > >Same problem. Add some realistic ESR and stray capacity and the F/2 signal >disappears.In a university campus, in a galaxy far, far away...... RL
Reply by ●November 11, 20152015-11-11
On 11/11/2015 07:03 AM, krw wrote:> On Tue, 10 Nov 2015 20:01:54 -0800, John Larkin > <jjlarkin@highlandtechnology.com> wrote: > >> On Tue, 10 Nov 2015 21:46:10 -0500, krw <krw@nowhere.com> wrote: >> >>> On Tue, 10 Nov 2015 21:23:26 -0500, legg <legg@nospam.magma.ca> wrote: >>> >>>> On Tue, 10 Nov 2015 23:02:39 +0100, jeroen Belleman >>>> <jeroen@nospam.please> wrote: >>>> >>>>> On 10/11/15 21:53, legg wrote: >>>>>> On Mon, 09 Nov 2015 23:16:51 +0100, jeroen Belleman >>>>>> <jeroen@nospam.please> wrote: >>>>>> >>>>>>> On 09/11/15 13:08, Phil Hobbs wrote: >>>>>>>> The paper I linked to (paywall unfortunately) talks about optimizing >>>>>>>> frequency halvers based on varactors and schottkys. >>>>>>>> >>>>>>>> All you need is a nonlinear capacitance, which all diodes have, and >>>>>>>> low enough loss. >>>>>>>> [...] >>>>>>> >>>>>>> >>>>>>> OK, I give in. Here is a simple circuit that generates a strong and >>>>>>> persistent f/2 from an input at frequency f. >>>>>>> >>>>>>> Jeroen Belleman >>>>>> >>>>>> Check your source impedance/current. Is it a fair trade? >>>>>> >>>>>> RL >>>>>> >>>>> >>>>> Not the point. The argument was about using parametric effects to >>>>> make oscillators. >>>>> >>>>> Come to think of it, I posted about another such thing, in an >>>>> argument over using mains-frequency driven magnet coils to sustain >>>>> a pendulum swinging at a ~1s period. That was a parametric >>>>> oscillator too. >>>>> >>>>> Jeroen Belleman >>>> >>>> It's not gain. >>>> >>> It's not an oscillator, either. >> >> The 60 Hz pump trick adds energy to the resonant device, the pendulum, >> just as a transistor (or a varicap pump) adds energy to an LC. Adding >> energy keeps the oscillation from dying out. >> >> A pumped resonator is an oscillator. As a bonus, the parametric >> oscillator is phase-locked to the pump. >> > You obviously consider the pendulum an oscillator but I think you're > alone. I see it as nothing more than a tank. There is no > amplification or feedback. What's the transfer equation? >You don't think that something that oscillates is an oscillator? Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●November 11, 20152015-11-11
On 11/11/2015 07:06 AM, krw wrote:> On Tue, 10 Nov 2015 20:01:54 -0800, John Larkin > <jjlarkin@highlandtechnology.com> wrote: > >> On Tue, 10 Nov 2015 21:46:10 -0500, krw <krw@nowhere.com> wrote: >> >>> On Tue, 10 Nov 2015 21:23:26 -0500, legg <legg@nospam.magma.ca> wrote: >>> >>>> On Tue, 10 Nov 2015 23:02:39 +0100, jeroen Belleman >>>> <jeroen@nospam.please> wrote: >>>> >>>>> On 10/11/15 21:53, legg wrote: >>>>>> On Mon, 09 Nov 2015 23:16:51 +0100, jeroen Belleman >>>>>> <jeroen@nospam.please> wrote: >>>>>> >>>>>>> On 09/11/15 13:08, Phil Hobbs wrote: >>>>>>>> The paper I linked to (paywall unfortunately) talks about optimizing >>>>>>>> frequency halvers based on varactors and schottkys. >>>>>>>> >>>>>>>> All you need is a nonlinear capacitance, which all diodes have, and >>>>>>>> low enough loss. >>>>>>>> [...] >>>>>>> >>>>>>> >>>>>>> OK, I give in. Here is a simple circuit that generates a strong and >>>>>>> persistent f/2 from an input at frequency f. >>>>>>> >>>>>>> Jeroen Belleman >>>>>> >>>>>> Check your source impedance/current. Is it a fair trade? >>>>>> >>>>>> RL >>>>>> >>>>> >>>>> Not the point. The argument was about using parametric effects to >>>>> make oscillators. >>>>> >>>>> Come to think of it, I posted about another such thing, in an >>>>> argument over using mains-frequency driven magnet coils to sustain >>>>> a pendulum swinging at a ~1s period. That was a parametric >>>>> oscillator too. >>>>> >>>>> Jeroen Belleman >>>> >>>> It's not gain. >>>> >>> It's not an oscillator, either. >> >> The 60 Hz pump trick adds energy to the resonant device, the pendulum, >> just as a transistor (or a varicap pump) adds energy to an LC. Adding >> energy keeps the oscillation from dying out. >> >> A pumped resonator is an oscillator. As a bonus, the parametric >> oscillator is phase-locked to the pump. >> > I don't see it as being phase locked, any more than an LC is phase > locked (its dual), either. >If you add an idler resonator, you can make a paramp with gain anywhere you like (below the pump frequency). There's an additional degree of freedom then, so there's no necessary phase relationship between the output and the pump, except that idler phase + output phase = pump phase. The pendulum is really an injection-locked system rather than a phase-locked one, if one wants to be pedantic about it. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●November 11, 20152015-11-11
On 11/11/2015 12:33 PM, Bruce S wrote:> legg <legg@nospam.magma.ca> wrote: > >> Why bother using a varicap? It's spice, after all. > > Same problem. Add some realistic ESR and stray capacity and the F/2 signal > disappears. >Not true in general. You can buy frequency halvers, no problem. Making the varactor a smaller part of the tank capacitance fixes it. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●November 11, 20152015-11-11
On 11/11/2015 12:29 PM, Bruce S wrote:> Phil Hobbs <pcdhobbs@gmail.com> wrote: > >> Helical and coaxial resonators can easily hit Qs of 600. >> >> Cheers >> >> Phil Hobbs >> > > Yes, John has mentioned that before. > > Doesn't do any good. You can change the series resistance in the ASC file I > posted to give a Q of 600. Increase the time to 5us. The oscillations peter > out in about 2us. > > The F/2 signal is merely an artifact of the startup transient. The circuit > does not generate a continuous F/2 signal. > > I am doing further studies on the MV2201 varactor ESR. The datasheet says > the series resistance (Rs) is 5.41 ohms. A simple series resonant circuit > in LTspice shows the ESR is abot 1.01 ohms at 0.25V bias. So there appears > to be a discrepancy between the datasheet and the SPICE model. >I invite you to read the paper I linked, about how to optimize a circuit that you appear to be claiming is impossible. Because that one is behind a paywall, I've posted a several-page excerpt from the ARRL VHF Handbook, First Ed. (1965) about how paramps work and how to build them. 'taint rocket surgery. http://electrooptical.net/www/sed/ARRLparamps.pdf Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●November 11, 20152015-11-11
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> On 11/11/2015 12:29 PM, Bruce S wrote:>> The F/2 signal is merely an artifact of the startup transient. The >> circuit does not generate a continuous F/2 signal.> I invite you to read the paper I linked, about how to optimize a > circuit that you appear to be claiming is impossible.> Because that one is behind a paywall, I've posted a several-page > excerpt from the ARRL VHF Handbook, First Ed. (1965) about how paramps > work and how to build them. 'taint rocket surgery.> http://electrooptical.net/www/sed/ARRLparamps.pdfParametric amplifiers are well-known. The paper you reference talks about a down converter that requires a signal input, a pump signal, and the output. That requires two input signals to generate the lower output frequency, similar to a mixer. They do not have a single varactor and inductor with a single input frequency as shown in Jeroen's circuit. I don't understand your statement that I claim the circuit is impossible. Of course you can run anything in LTspice. You don't have to include realistic stray capacitances and impedances. That doesn't mean it will work on the bench. The circuit I posted shows the F/2 signal dies out in a few cycles when you include realistic ESR and stray capacitances. Please post a circuit showing how to optimize a single varactor and inductor as in Jeroen's circuit to produce a sub-multiple of a single input signal.> Cheers > > Phil Hobbs >
Reply by ●November 11, 20152015-11-11
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:> On 11/11/2015 12:33 PM, Bruce S wrote: >> legg <legg@nospam.magma.ca> wrote: >> >>> Why bother using a varicap? It's spice, after all. >> >> Same problem. Add some realistic ESR and stray capacity and the F/2 >> signal disappears. >> > > Not true in general. You can buy frequency halvers, no problem. > Making the varactor a smaller part of the tank capacitance fixes it.I am unable to find commercial versions of a frequency halver. Can you supply some links? In Legg's circuit, as soon as you add realistic ESR and stray capacitance across the inductor, the F/2 signal disappears> Cheers > > Phil Hobbs >
