On Wednesday, April 28, 2021 at 2:09:47 PM UTC-7, jla...@highlandsniptechnology.com wrote:> I'd prefer to use a MMIC, but there seem to be no spice models for > mmics. Mini-Circuits was adamant that they would never have spice > models for theirs...Because they want to be able to switch parts or even vendors at the drop of a hat. People tend to forget that Mini-Circuits doesn't actually make chips. -- john, KE5FX (yes, this has hosed me before)
GHz oscillator
Started by ●April 27, 2021
Reply by ●April 28, 20212021-04-28
Reply by ●April 28, 20212021-04-28
On Wed, 28 Apr 2021 15:10:07 -0700 (PDT), "John Miles, KE5FX" <jmiles@gmail.com> wrote:>On Wednesday, April 28, 2021 at 2:09:47 PM UTC-7, jla...@highlandsniptechnology.com wrote: >> I'd prefer to use a MMIC, but there seem to be no spice models for >> mmics. Mini-Circuits was adamant that they would never have spice >> models for theirs... > >Because they want to be able to switch parts or even vendors at the >drop of a hat. People tend to forget that Mini-Circuits doesn't actually >make chips. > >-- john, KE5FX >(yes, this has hosed me before)We got burned once when their parts (ERA-5?) changed radically. -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 29, 20212021-04-29
On Wed, 28 Apr 2021 23:53:20 +0200, Jeroen Belleman <jeroen@nospam.please> wrote:>On 2021-04-28 23:46, upsidedown@downunder.com wrote: >> On Wed, 28 Apr 2021 14:09:37 -0700, jlarkin@highlandsniptechnology.com >> wrote: >> >>> On Wed, 28 Apr 2021 13:37:13 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>> >>>> jlarkin@highlandsniptechnology.com wrote: >>>>> On Wed, 28 Apr 2021 13:05:32 +1000, Clifford Heath >>>>> <no.spam@please.net> wrote: >>>>> >>>>>> On 28/4/21 5:35 am, John Larkin wrote: >>>>>>> What's a good way to make a, say 2 or 3 GHz sinewave oscillator? >>>>>> >>>>>> Accidentally? >>>>>> >>>>>> :) >>>>> >>>>> I just posted an accidental 3 GHz phemt oscillator. >>>>> >>>>> Purely fiddled in Spice in a few minutes; all instinct, no theory at >>>>> all. Reasonably good sine wave. >>>>> >>>>> >>>>> >>>> >>>> Ungodly amount of gate current, though--abs max is 2 mA. >>> >>> Good point; that's fixable. >>> >>>> >>>> Cheers >>>> >>>> Phil Hobbs >>> >>> I'd prefer to use a MMIC, but there seem to be no spice models for >>> mmics. Mini-Circuits was adamant that they would never have spice >>> models for theirs. >> >> They specify the S-parameters so you can figure out how much more >> phase shift is needed on the desired frequency to satisfy the >> Barkhausen criterion. Of course you have to check that the forward >> gain is larger than feedback network losses to have a sustained >> oscillation at desired frequency. > >MMICs are basically Darlingtons. I suppose a Colpitts arrangement >should work.At least with ordinary MAR-x MMICs, the frequency is quite high and hence the parameters are quite non-ideal, so you may have to consult the Smith chart to make it work reliably.>Jeroen Belleman
Reply by ●April 29, 20212021-04-29
On Thu, 29 Apr 2021 07:32:04 +0300, upsidedown@downunder.com wrote:>On Wed, 28 Apr 2021 23:53:20 +0200, Jeroen Belleman ><jeroen@nospam.please> wrote: > >>On 2021-04-28 23:46, upsidedown@downunder.com wrote: >>> On Wed, 28 Apr 2021 14:09:37 -0700, jlarkin@highlandsniptechnology.com >>> wrote: >>> >>>> On Wed, 28 Apr 2021 13:37:13 -0400, Phil Hobbs >>>> <pcdhSpamMeSenseless@electrooptical.net> wrote: >>>> >>>>> jlarkin@highlandsniptechnology.com wrote: >>>>>> On Wed, 28 Apr 2021 13:05:32 +1000, Clifford Heath >>>>>> <no.spam@please.net> wrote: >>>>>> >>>>>>> On 28/4/21 5:35 am, John Larkin wrote: >>>>>>>> What's a good way to make a, say 2 or 3 GHz sinewave oscillator? >>>>>>> >>>>>>> Accidentally? >>>>>>> >>>>>>> :) >>>>>> >>>>>> I just posted an accidental 3 GHz phemt oscillator. >>>>>> >>>>>> Purely fiddled in Spice in a few minutes; all instinct, no theory at >>>>>> all. Reasonably good sine wave. >>>>>> >>>>>> >>>>>> >>>>> >>>>> Ungodly amount of gate current, though--abs max is 2 mA. >>>> >>>> Good point; that's fixable. >>>> >>>>> >>>>> Cheers >>>>> >>>>> Phil Hobbs >>>> >>>> I'd prefer to use a MMIC, but there seem to be no spice models for >>>> mmics. Mini-Circuits was adamant that they would never have spice >>>> models for theirs. >>> >>> They specify the S-parameters so you can figure out how much more >>> phase shift is needed on the desired frequency to satisfy the >>> Barkhausen criterion. Of course you have to check that the forward >>> gain is larger than feedback network losses to have a sustained >>> oscillation at desired frequency. >> >>MMICs are basically Darlingtons. I suppose a Colpitts arrangement >>should work. > >At least with ordinary MAR-x MMICs, the frequency is quite high and >hence the parameters are quite non-ideal, so you may have to consult >the Smith chart to make it work reliably.All those s-params are basically useless when you want to use an RF part in time domain, namely large-signal nonlinear. Even DC behavior is usually poorly defined. Some RF data sheets show a bias trimpot and say "turn the pot until it works." One has to breadboard and measure to understand the DC and nonlinear behavior of things like MMICs. You are lucky to get any DC curves on an RF fet data sheet. The SAV series is a welcome exception, and I measured more. A Spice model would be far better than tables of S-params. S-params can be derived from a Spice model, but not the reverse. I think a lot of RF design was created for the pre-computer days. The max voltage ratings of RF parts seem to (sometimes) assume that peak voltage will be some multiple of supply voltage, and the spec is actually max supply voltage. Sometimes. We've used 7-volt rated parts at 25 volts peak and they were fine. -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 29, 20212021-04-29
Cryteck (not right spelling but close) makes some in that range at ~$25 apiece. I have one currently that outputs 1 to 2 ghz. Power supply is 10 volts @ 25 ma and the frequency selection is 1v to 20v. It's recieved some tough handling and some excessive soldering & it's still working like a trooper... It's built on a 1/32 alumina board. Both Digikey & Mouser carry them. Hul John Larkin <jlarkin@highland_atwork_technology.com> wrote:> What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I > don't need extreme accuracy, and I'd like maybe 1 volt p-p.> I was thinking a cheap MMIC with PCB delay line feedback.> MiniCircuits VCOs are around $20, which isn't bad.> The output would go into a PWM modulator and then an AC-coupled > communications channel.
Reply by ●April 30, 20212021-04-30
On Tue, 27 Apr 2021 12:35:17 -0700, John Larkin <jlarkin@highland_atwork_technology.com> wrote:>What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I >don't need extreme accuracy, and I'd like maybe 1 volt p-p. > >I was thinking a cheap MMIC with PCB delay line feedback. > >MiniCircuits VCOs are around $20, which isn't bad. > >The output would go into a PWM modulator and then an AC-coupled >communications channel.hat are you trying to do ? Are you trying to transfer a very broad band DC based _analog_ signal (say DC .. 500 MHz) over an AC link (say 2 GHz). Why not simply frequency module a VCO ? Why PWM ?
Reply by ●April 30, 20212021-04-30
fredag den 30. april 2021 kl. 07.07.16 UTC+2 skrev upsid...@downunder.com:> On Tue, 27 Apr 2021 12:35:17 -0700, John Larkin > <jlarkin@highland_atwork_technology.com> wrote: > >What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I > >don't need extreme accuracy, and I'd like maybe 1 volt p-p. > > > >I was thinking a cheap MMIC with PCB delay line feedback. > > > >MiniCircuits VCOs are around $20, which isn't bad. > > > >The output would go into a PWM modulator and then an AC-coupled > >communications channel. > hat are you trying to do ? > > Are you trying to transfer a very broad band DC based _analog_ signal > (say DC .. 500 MHz) over an AC link (say 2 GHz). > > Why not simply frequency module a VCO ? Why PWM ?easy demodulation?
Reply by ●April 30, 20212021-04-30
On Fri, 30 Apr 2021 08:07:10 +0300, upsidedown@downunder.com wrote:>On Tue, 27 Apr 2021 12:35:17 -0700, John Larkin ><jlarkin@highland_atwork_technology.com> wrote: > >>What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I >>don't need extreme accuracy, and I'd like maybe 1 volt p-p. >> >>I was thinking a cheap MMIC with PCB delay line feedback. >> >>MiniCircuits VCOs are around $20, which isn't bad. >> >>The output would go into a PWM modulator and then an AC-coupled >>communications channel. > >hat are you trying to do ? > >Are you trying to transfer a very broad band DC based _analog_ signal >(say DC .. 500 MHz) over an AC link (say 2 GHz).That, or just ship a single-bit logic level over a telecom type link. It's just a shower musing, not serious yet.> >Why not simply frequency module a VCO ? Why PWM ? >FM is more work on both ends. Commercial VCOs have pitiful modulation bandwidths, kilohertz not gigahertz. PWM can be arbitrarily fast. For the logic level case, we'd want it to be fast with low jitter. Whatever modulation scheme is used, the time jitter should be a fraction of the "carrier" period. This problem is similar to the Shannon sampling theorem. A bandlimited signal can be sampled at some rate and reproduced perfectly from the sampled values. The trick is to have the modulation scheme be continuous and bandlimited such as to eliminate the jitter of the modulation/demod scheme. Wideband FM gets mathematically messy too. Ugly sidebands. PWM would be fairly easy to generate and detect. I've tested some 10 GBPS tosa/rosa optical links and they do transmit PWM, to various extents. Of course they go bonkers at extreme duty cycles. -- John Larkin Highland Technology, Inc The best designs are necessarily accidental.
Reply by ●April 30, 20212021-04-30
On Fri, 30 Apr 2021 08:13:48 -0700 (PDT), Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:>fredag den 30. april 2021 kl. 07.07.16 UTC+2 skrev upsid...@downunder.com: >> On Tue, 27 Apr 2021 12:35:17 -0700, John Larkin >> <jlarkin@highland_atwork_technology.com> wrote: >> >What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I >> >don't need extreme accuracy, and I'd like maybe 1 volt p-p. >> > >> >I was thinking a cheap MMIC with PCB delay line feedback. >> > >> >MiniCircuits VCOs are around $20, which isn't bad. >> > >> >The output would go into a PWM modulator and then an AC-coupled >> >communications channel. >> hat are you trying to do ? >> >> Are you trying to transfer a very broad band DC based _analog_ signal >> (say DC .. 500 MHz) over an AC link (say 2 GHz). >> >> Why not simply frequency module a VCO ? Why PWM ? > >easy demodulation?What is the problem with a simple FM-demulator ? At the transmitter site just insert some sync pulses that goes to 0 V into the analog input of the VCO. At the receiver site, after the FM demodulator, a simple capacitor/diode circuit s used to restore the 0 V DC level, thus compensating for VCO drift. Think about analog composite video processing.
Reply by ●April 30, 20212021-04-30
On Fri, 30 Apr 2021 08:45:30 -0700, jlarkin@highlandsniptechnology.com wrote:>On Fri, 30 Apr 2021 08:07:10 +0300, upsidedown@downunder.com wrote: > >>On Tue, 27 Apr 2021 12:35:17 -0700, John Larkin >><jlarkin@highland_atwork_technology.com> wrote: >> >>>What's a good way to make a, say 2 or 3 GHz sinewave oscillator? I >>>don't need extreme accuracy, and I'd like maybe 1 volt p-p. >>> >>>I was thinking a cheap MMIC with PCB delay line feedback. >>> >>>MiniCircuits VCOs are around $20, which isn't bad. >>> >>>The output would go into a PWM modulator and then an AC-coupled >>>communications channel. >> >>hat are you trying to do ? >> >>Are you trying to transfer a very broad band DC based _analog_ signal >>(say DC .. 500 MHz) over an AC link (say 2 GHz). > > >That, or just ship a single-bit logic level over a telecom type link. >It's just a shower musing, not serious yet. > >> >>Why not simply frequency module a VCO ? Why PWM ? >> > >FM is more work on both ends. Commercial VCOs have pitiful modulation >bandwidths, kilohertz not gigahertz. PWM can be arbitrarily fast. > >For the logic level case, we'd want it to be fast with low jitter. >Whatever modulation scheme is used, the time jitter should be a >fraction of the "carrier" period.What about phase shifting keying (PSK) ? Just invert the output from the oscillator at input signal change. Of course, you have to establish the initial state somehow to be able to decode current state from only phase changes. To always know the state, you could use return to zero coding, i.e. a carrier at 0 degrees, a 0->1 transition as +90 degree phase change and 1->0 input change as -90 degrees phase shift (QPSK). Also take look at Manchester coding.
