On 11/09/2015 01:59 PM, 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 >Arm waving explanation: In an LC paramp, you want the capacitance to be decreasing as the output goes through its +-peak values, and increasing at the zero crossings. (A varactor wired across a bridge rectifier is one example of a device that does this. Two varactors back-to-back also work.) The voltage goes as 1/C, and the energy in the capacitor goes as CV**2, so at the peaks dE/dt = E/C dC/dt. The circuit will oscillate at f/2 by building up from noise, provided that the input is strong enough to make the loop gain at f/2 more than unity. The output will be loosely phase locked with the input, of course, because the gain isn't a very strong function of the relative phase. 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
Magamp oscillator
Started by ●November 3, 2015
Reply by ●November 9, 20152015-11-09
Reply by ●November 9, 20152015-11-09
"Phil Hobbs" wrote in message news:I7udnepF_KCguNzLnZ2dnUU7-aOdnZ2d@supernews.com...>Arm waving explanation: > >In an LC paramp, you want the capacitance to be decreasing as the output >goes through its +-peak values, and increasing at the zero crossings. (A >varactor wired across a bridge rectifier is one example of a device that >does this. Two varactors back-to-back also work.) > >The voltage goes as 1/C, and the energy in the capacitor goes as CV**2, >so at the peaks > >dE/dt = E/C dC/dt. > >The circuit will oscillate at f/2 by building up from noise, provided >that the input is strong enough to make the loop gain at f/2 more than >unity. The output will be loosely phase locked with the input, of >course, because the gain isn't a very strong function of the relative >phase. >How do you wire that? An L || C only has one resonant mode, and no isolation. Would you use one resonator for the pump, one for the signal frequency, and span the "funky C" between them? And then the signal resonator then looks like a negative resistance, so you have to come up with your own hybrid / isolator / circulator / etc. to get an amplifier as such? (The magamp equivalent would be two resonators, where the caps go to a common ground, except it's not ground, it's the magamp core.) How does one relate the impedances of such a circuit? The resonator frequencies are defined by their LC components, plus the average capacitance (more or less, and I suppose, give or take if the pump and signal are correlated or not), and the pump magnitude is something about the (Cmin / CJO) ratio and resonator impedances and Qs. Does it only work at f/2? That seems rather less useful, needing an oscillator at a much higher frequency all the time. (Of course, doublers and triplers, of modest efficiency, are a thing. Often using varactors again, it seems. But a stack of those gets rather wasteful.) After all, magnetrons can be modulated, and that's old fashioned, like 10GHz in the 1950s, late 40s even. Though it's not like you can phase lock a magnetron to a quartz oscillator (or better)... I suppose that's the point, the pump can be any dirty old AC (give or take "PSRR"), while the signal is something cleaner. As for "degenerate", I presume that's something about being able to handle DC (or most anything between DC and Fp/2)? Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reply by ●November 9, 20152015-11-09
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 > >======== Cut here ======== >Version 4 >SHEET 1 880 680 >WIRE 240 80 144 80 >WIRE 288 80 240 80 >WIRE 144 96 144 80 >WIRE 288 128 288 80 >WIRE 144 208 144 160 >WIRE 144 208 96 208 >WIRE 144 256 144 208 >WIRE 288 272 288 208 >WIRE 144 352 144 336 >FLAG 288 272 0 >FLAG 144 352 0 >FLAG 240 80 tank >FLAG 96 208 pump >SYMBOL varactor 128 96 R0 >SYMATTR InstName D1 >SYMATTR Value MV2201 >SYMBOL ind 272 112 R0 >SYMATTR InstName L1 >SYMATTR Value 1? >SYMBOL voltage 144 240 R0 >WINDOW 123 0 0 Left 2 >WINDOW 39 0 0 Left 2 >SYMATTR InstName V1 >SYMATTR Value SINE(1 1 96.08meg) >TEXT 176 24 Left 2 !.tran 10uOoh, that's nice. The varicap is the nonlinear thing and the tank capacitor simultaneously. I had to change the L value to 1 uH; the "mu" symbol didn't survive Usenet. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●November 10, 20152015-11-10
On 09/11/2015 20:30, John Larkin wrote:> It sounds like there was a telephone central-office 20 Hz ring > generator that was a magamp based divide-by-3, off the 60 Hz line. > >Yes. The best known is possibly the Lorain Sub-cycler family: <http://www.telephonecollectors.info/index.php/document-repository/cat_view/185-bruce-crawford-library/198-lorain-products> The "decimonic" K5 produced 20Hz and 30Hz by para-amp action and then mixed to generate 40Hz and 50Hz (10Hz spacing=decimonic) by a demonic circuit shown in the download fig 8. piglet
Reply by ●November 10, 20152015-11-10
jeroen Belleman 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 > >======== Cut here ======== >Version 4 >SHEET 1 880 680 >WIRE 240 80 144 80 >WIRE 288 80 240 80 >WIRE 144 96 144 80 >WIRE 288 128 288 80 >WIRE 144 208 144 160 >WIRE 144 208 96 208 >WIRE 144 256 144 208 >WIRE 288 272 288 208 >WIRE 144 352 144 336 >FLAG 288 272 0 >FLAG 144 352 0 >FLAG 240 80 tank >FLAG 96 208 pump >SYMBOL varactor 128 96 R0 >SYMATTR InstName D1 >SYMATTR Value MV2201 >SYMBOL ind 272 112 R0 >SYMATTR InstName L1 >SYMATTR Value 1� >SYMBOL voltage 144 240 R0 >WINDOW 123 0 0 Left 2 >WINDOW 39 0 0 Left 2 >SYMATTR InstName V1 >SYMATTR Value SINE(1 1 96.08meg) >TEXT 176 24 Left 2 !.tran 10uIs that LTSpice? It complains, Multiple instances of "Flag" -- Thanks, - Win
Reply by ●November 10, 20152015-11-10
On 2015-11-10 14:14, Winfield Hill wrote:> jeroen Belleman 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 >> >> ======== Cut here ======== >> Version 4 >> SHEET 1 880 680 >> WIRE 240 80 144 80 >> WIRE 288 80 240 80 >> WIRE 144 96 144 80 >> WIRE 288 128 288 80 >> WIRE 144 208 144 160 >> WIRE 144 208 96 208 >> WIRE 144 256 144 208 >> WIRE 288 272 288 208 >> WIRE 144 352 144 336 >> FLAG 288 272 0 >> FLAG 144 352 0 >> FLAG 240 80 tank >> FLAG 96 208 pump >> SYMBOL varactor 128 96 R0 >> SYMATTR InstName D1 >> SYMATTR Value MV2201 >> SYMBOL ind 272 112 R0 >> SYMATTR InstName L1 >> SYMATTR Value 1� >> SYMBOL voltage 144 240 R0 >> WINDOW 123 0 0 Left 2 >> WINDOW 39 0 0 Left 2 >> SYMATTR InstName V1 >> SYMATTR Value SINE(1 1 96.08meg) >> TEXT 176 24 Left 2 !.tran 10u > > Is that LTSpice? It complains, Multiple instances of "Flag" > >Yes indeed. It doesn't complain here. OK, I declined to upgrade LTspice since almost four years. Some asc file format changes may have occurred since. Beware of the value of L1: It should be 1uH. The 'mu' doesn't fare well on Usenet. Sorry about that. I just fix that using a text editor when it happens to me. Here's an ASCII version of the schematic: tank +-----------+ | | | | V MV2201 L = varicap L | L 1u | | - | / \ | | V | GND \ / | V=1+sine(97MHz) (pump) | GND Next challenge: A circuit that produces two *different* frequencies, such that f1+f2=fpump. Jeroen Belleman
Reply by ●November 10, 20152015-11-10
On 10 Nov 2015 05:14:54 -0800, Winfield Hill <hill@rowland.harvard.edu> wrote:>jeroen Belleman 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 >> >>======== Cut here ======== >>Version 4 >>SHEET 1 880 680 >>WIRE 240 80 144 80 >>WIRE 288 80 240 80 >>WIRE 144 96 144 80 >>WIRE 288 128 288 80 >>WIRE 144 208 144 160 >>WIRE 144 208 96 208 >>WIRE 144 256 144 208 >>WIRE 288 272 288 208 >>WIRE 144 352 144 336 >>FLAG 288 272 0 >>FLAG 144 352 0 >>FLAG 240 80 tank >>FLAG 96 208 pump >>SYMBOL varactor 128 96 R0 >>SYMATTR InstName D1 >>SYMATTR Value MV2201 >>SYMBOL ind 272 112 R0 >>SYMATTR InstName L1 >>SYMATTR Value 1� >>SYMBOL voltage 144 240 R0 >>WINDOW 123 0 0 Left 2 >>WINDOW 39 0 0 Left 2 >>SYMATTR InstName V1 >>SYMATTR Value SINE(1 1 96.08meg) >>TEXT 176 24 Left 2 !.tran 10u > > Is that LTSpice? It complains, Multiple instances of "Flag"I ran it in the current LT Spice, except that ? should be u. It's amazing. Divides by 2 with gain!
Reply by ●November 10, 20152015-11-10
On 10.11.15 15:14, Winfield Hill wrote:> jeroen Belleman 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 >> >> ======== Cut here ======== >> Version 4 >> SHEET 1 880 680 >> WIRE 240 80 144 80 >> WIRE 288 80 240 80 >> WIRE 144 96 144 80 >> WIRE 288 128 288 80 >> WIRE 144 208 144 160 >> WIRE 144 208 96 208 >> WIRE 144 256 144 208 >> WIRE 288 272 288 208 >> WIRE 144 352 144 336 >> FLAG 288 272 0 >> FLAG 144 352 0 >> FLAG 240 80 tank >> FLAG 96 208 pump >> SYMBOL varactor 128 96 R0 >> SYMATTR InstName D1 >> SYMATTR Value MV2201 >> SYMBOL ind 272 112 R0 >> SYMATTR InstName L1 >> SYMATTR Value 1� >> SYMBOL voltage 144 240 R0 >> WINDOW 123 0 0 Left 2 >> WINDOW 39 0 0 Left 2 >> SYMATTR InstName V1 >> SYMATTR Value SINE(1 1 96.08meg) >> TEXT 176 24 Left 2 !.tran 10u > > Is that LTSpice? It complains, Multiple instances of "Flag"It works here in LTSpice, after correcting the value of L1 to 1u. -- -TV
Reply by ●November 10, 20152015-11-10
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
Reply by ●November 10, 20152015-11-10
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 BellemanIt's not gain. RL
