Re: [time-nuts] reference oscillator input circuit
Javier Herrero wrote: I was thinking about how good or how bad would result the use of an LVDS line receiver ... but it is only a though :) That's what I was using before, and it doesn't work very well.. Small common mode voltage range and large hysteresis. They're really designed to take square wave(ish) inputs. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Chris Albertson wrote: Of all the ways to square a sine wave I think the best might be to use a PLL. the raising edge of your output square wave would trigger a sample of the input sine wave. The distance from zero volts of that sample is the phase error. The goal is to have the raising edge of the square wave happen just as the sine crosses zero. But if it's not dead-on you get an error signal that can be either positive or negative and this error is low pass filtered and then applied as a correction. But my guess is that if you are using this to feed a 'scope a reference frequency the scope will have it's own PLL. No, actually to feed a bunch of synthesizer chains (for which the sine wave will work fine) and to drive sampling clocks on ADC/DAC (for which one wants a low jitter square wave). A digital radio... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Good to know. Now I see what not to use :) I was supposing that the hysteresis would not be so high being low voltage signalling, and since they are used for low-jitter applications. But really I've only used them for their intended main applications :) Best regards, Javier El 09/12/2010 14:50, jimlux escribió: Javier Herrero wrote: I was thinking about how good or how bad would result the use of an LVDS line receiver ... but it is only a though :) That's what I was using before, and it doesn't work very well.. Small common mode voltage range and large hysteresis. They're really designed to take square wave(ish) inputs. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Javier Herrero wrote: Good to know. Now I see what not to use :) I was supposing that the hysteresis would not be so high being low voltage signalling, and since they are used for low-jitter applications. But really I've only used them for their intended main applications :) hysteresis is in the 100mV minimum range, and max peak amplitude is in the 0.9 to 1 Volt range (they'll have a bias point a bit over a volt, and a lot of them do not do well at all if you swing close to the supply rail) Maybe with external clamps and over drive it. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
El 09/12/2010 15:21, jimlux escribió: Javier Herrero wrote: Good to know. Now I see what not to use :) I was supposing that the hysteresis would not be so high being low voltage signalling, and since they are used for low-jitter applications. But really I've only used them for their intended main applications :) hysteresis is in the 100mV minimum range, and max peak amplitude is in the 0.9 to 1 Volt range (they'll have a bias point a bit over a volt, and a lot of them do not do well at all if you swing close to the supply rail) Maybe with external clamps and over drive it. Yes, I was thinking in that way. But surely they are better solutions :) Regards, Javier -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Javier Herrero wrote: El 09/12/2010 15:21, jimlux escribió: Javier Herrero wrote: Good to know. Now I see what not to use :) I was supposing that the hysteresis would not be so high being low voltage signalling, and since they are used for low-jitter applications. But really I've only used them for their intended main applications :) hysteresis is in the 100mV minimum range, and max peak amplitude is in the 0.9 to 1 Volt range (they'll have a bias point a bit over a volt, and a lot of them do not do well at all if you swing close to the supply rail) Maybe with external clamps and over drive it. Yes, I was thinking in that way. But surely they are better solutions :) hence my question to the list.. I'm going to gather all the responses and summarize them for the list later today. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
jimlux wrote: Javier Herrero wrote: El 09/12/2010 15:21, jimlux escribió: Javier Herrero wrote: Good to know. Now I see what not to use :) I was supposing that the hysteresis would not be so high being low voltage signalling, and since they are used for low-jitter applications. But really I've only used them for their intended main applications :) hysteresis is in the 100mV minimum range, and max peak amplitude is in the 0.9 to 1 Volt range (they'll have a bias point a bit over a volt, and a lot of them do not do well at all if you swing close to the supply rail) Maybe with external clamps and over drive it. Yes, I was thinking in that way. But surely they are better solutions :) hence my question to the list.. I'm going to gather all the responses and summarize them for the list later today. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. Since noise modulation (power supply and device noise) of device parameters (eg collector base capacitance) can be a significant source of phase noise adding some emitter degeneration in a long tailed pair and shunting the collector load resistors with inductors (eg a transformer winding) should be an effective way of reducing such phase noise. A capacitor shunting the collector load can also be effective in reducing the circuit bandwidth closer to the optimum and desensitising the circuit bandwidth to device parameter variations. However avoiding high Q parasitic resonances with the output inductors (or transformer) will be necessary. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
No, actually to feed a bunch of synthesizer chains (for which the sine wave will work fine) and to drive sampling clocks on ADC/DAC (for which one wants a low jitter square wave). A digital radio... There are some nice residual plots for AC and CMOS chips at http://www.xs4all.nl/~martein/pa3ake/hmode/dds_ad9910_pmnoise.html . Seems like the AD9515 family in PECL mode is about as good as anything is likely to get at VHF. However, why not use the sine wave directly, converted to differential with a transformer and clipped by back-to-back Schottkys? At VHF clock frequencies any active sine-to-square conversion circuit I'm aware of will contribute more jitter than the ADC's own tJ spec. (Put another way, if I'm a semiconductor house designing a high-end ADC or DAC, I am probably going to put all the secret sauce I have into the on-chip clock conditioning, leaving little or no room for improvement outside the chip.) The eval boards from the various ADC manufacturers bear this out. No one puts anything but a 50-ohm SMA jack, transformer and Schottkys on their clock inputs. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Hi ...and sometimes they leave the Schottkys out. The original request was not a really low jitter application. I think Jim can get away with an active circuit. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of John Miles Sent: Thursday, December 09, 2010 4:00 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] reference oscillator input circuit No, actually to feed a bunch of synthesizer chains (for which the sine wave will work fine) and to drive sampling clocks on ADC/DAC (for which one wants a low jitter square wave). A digital radio... There are some nice residual plots for AC and CMOS chips at http://www.xs4all.nl/~martein/pa3ake/hmode/dds_ad9910_pmnoise.html . Seems like the AD9515 family in PECL mode is about as good as anything is likely to get at VHF. However, why not use the sine wave directly, converted to differential with a transformer and clipped by back-to-back Schottkys? At VHF clock frequencies any active sine-to-square conversion circuit I'm aware of will contribute more jitter than the ADC's own tJ spec. (Put another way, if I'm a semiconductor house designing a high-end ADC or DAC, I am probably going to put all the secret sauce I have into the on-chip clock conditioning, leaving little or no room for improvement outside the chip.) The eval boards from the various ADC manufacturers bear this out. No one puts anything but a 50-ohm SMA jack, transformer and Schottkys on their clock inputs. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John On 12/8/2010 10:31 AM, jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz -90dBc 10Hz -110dBc 100Hz -120dBc 1k-100k -125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
John Ackermann N8UR wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John Doh... I was thinking that there was some vendor with ap notes on stuff like this, and I couldn't recall who it was, and I'm actually looking at a Wenzel OCXO sitting here on the desk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). In the 5071A at 80 MHz, we capacitively coupled a sine wave into a 74AC series logic gate, that had DC bias resistors to hold it at half the supply voltage. Rick Karlquist ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
The document cited is full of plausible sounding but misleading information, if you want really low jitter. This type of oversimplification of the problem was present when the HP53131 series counters were designed, with the result that the Allan deviation of an external 10 MHz reference is degraded to only a part in 10^11 at 1 second. Rick Karlquist jimlux wrote: John Ackermann N8UR wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John Doh... I was thinking that there was some vendor with ap notes on stuff like this, and I couldn't recall who it was, and I'm actually looking at a Wenzel OCXO sitting here on the desk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Just an FYI guys, I'm pretty sure the 3rd circuit down on the Wenzel page is identical to the input circuit for the TAPR TADD-2 frequency divider. The TADD-2 adds a transformer and load resistor. Schematic is in the manual here: http://www.tapr.org/~n8ur/TADD-2_Manual.pdf -Bob On Wed, Dec 8, 2010 at 8:46 AM, John Ackermann N8UR j...@febo.com wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John On 12/8/2010 10:31 AM, jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz -90dBc 10Hz -110dBc 100Hz -120dBc 1k-100k -125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
I can confirm that -- that's where I found it (and my schematic in the TADD-2 manual gives credit to Wenzel)! I chose that design mainly because it worked over a wide range of input levels. John On 12/8/2010 12:48 PM, Robert Darlington wrote: Just an FYI guys, I'm pretty sure the 3rd circuit down on the Wenzel page is identical to the input circuit for the TAPR TADD-2 frequency divider. The TADD-2 adds a transformer and load resistor. Schematic is in the manual here: http://www.tapr.org/~n8ur/TADD-2_Manual.pdf -Bob On Wed, Dec 8, 2010 at 8:46 AM, John Ackermann N8URj...@febo.com wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John On 12/8/2010 10:31 AM, jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz-90dBc 10Hz-110dBc 100Hz-120dBc 1k-100k-125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Rick Karlquist wrote: jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). In the 5071A at 80 MHz, we capacitively coupled a sine wave into a 74AC series logic gate, that had DC bias resistors to hold it at half the supply voltage. that's similar to what Said recommended last year.. he uses a big resistor from output to input to set the bias, rather than a divider. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
One problem with this circuit is that tolerances in the resistors produce an offset between the 2 transistor bases in addition to any transistor mismatch, It's better to share a single divider and short (eg a transformer winding. Or at least connect them with a low impedance at low frequencies) the transistor bases together. Capacitively coupling the emitters can also be useful. Bruce Robert Darlington wrote: Just an FYI guys, I'm pretty sure the 3rd circuit down on the Wenzel page is identical to the input circuit for the TAPR TADD-2 frequency divider. The TADD-2 adds a transformer and load resistor. Schematic is in the manual here: http://www.tapr.org/~n8ur/TADD-2_Manual.pdf -Bob On Wed, Dec 8, 2010 at 8:46 AM, John Ackermann N8URj...@febo.com wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John On 12/8/2010 10:31 AM, jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz-90dBc 10Hz-110dBc 100Hz-120dBc 1k-100k-125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Assuming a transformer coupled input (with biasing via a secondary center tap) why not use a fast differential PECL to CMOS level translator? For example, the IDT ICS508 will take 0.3 to 1.0 V p-p input and give 2.5, 3.3, or 5 V swing on the output. The chip works down to DC and keeps the duty cycle in the 40%-60% window up to 250MHz (at 3.3V out). Jitter and noise is not spec'd however. To increase the noise immunity with a relatively slow 10MHz sine source I'd look at boosting the amplitude with the transformer, then clipping with balanced series resistors and back-to-back diodes so the translator sees a higher dV/dT on its inputs. Might want to look in some old Motorola ECL appnotes for other possible schemes. Bob From: jimlux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, December 8, 2010 10:31:08 AM Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz -90dBc 10Hz -110dBc 100Hz -120dBc 1k-100k -125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
One caveat with driving a CMOS gate input is that if it is overdriven so that the input protection circuit diodes conduct then the output jitter may increase substantially. At least this appears to happen when overdriving 74HC04 inverters. Once the input diodes conduct (5MHz sine wave input) the output jitter is easily measured with a 5370A/B. Just below conduction the output jitter appears to be buried in the 5370A/B noise. Bruce Rick Karlquist wrote: The document cited is full of plausible sounding but misleading information, if you want really low jitter. This type of oversimplification of the problem was present when the HP53131 series counters were designed, with the result that the Allan deviation of an external 10 MHz reference is degraded to only a part in 10^11 at 1 second. Rick Karlquist jimlux wrote: John Ackermann N8UR wrote: Wenzel has some discussion and circuits at: http://www.wenzel.com/documents/waveform.html. The Shera GPSDO made clever use of the input circuit of a 74HCT4046 PLL chip for squaring. John Doh... I was thinking that there was some vendor with ap notes on stuff like this, and I couldn't recall who it was, and I'm actually looking at a Wenzel OCXO sitting here on the desk. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
One can estimate the resultant jitter from the input slew rate and the circuit noise and bandwidth. Too much bandwidth with a slow input slew rate increases the jitter substantially over that possible with an optimal circuit. Bruce Robert LaJeunesse wrote: Assuming a transformer coupled input (with biasing via a secondary center tap) why not use a fast differential PECL to CMOS level translator? For example, the IDT ICS508 will take 0.3 to 1.0 V p-p input and give 2.5, 3.3, or 5 V swing on the output. The chip works down to DC and keeps the duty cycle in the 40%-60% window up to 250MHz (at 3.3V out). Jitter and noise is not spec'd however. To increase the noise immunity with a relatively slow 10MHz sine source I'd look at boosting the amplitude with the transformer, then clipping with balanced series resistors and back-to-back diodes so the translator sees a higher dV/dT on its inputs. Might want to look in some old Motorola ECL appnotes for other possible schemes. Bob From: jimluxjim...@earthlink.net To: Discussion of precise time and frequency measurementtime-nuts@febo.com Sent: Wed, December 8, 2010 10:31:08 AM Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz-90dBc 10Hz-110dBc 100Hz-120dBc 1k-100k-125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
ECL has a high phase noise floor in the -140s. Other than that, it works fine. Rick Karlquist Robert LaJeunesse wrote: Assuming a transformer coupled input (with biasing via a secondary center tap) why not use a fast differential PECL to CMOS level translator? For example, the IDT ICS508 will take 0.3 to 1.0 V p-p input and give 2.5, 3.3, or 5 V swing on the output. The chip works down to DC and keeps the duty cycle in the 40%-60% window up to 250MHz (at 3.3V out). Jitter and noise is not spec'd however. To increase the noise immunity with a relatively slow 10MHz sine source I'd look at boosting the amplitude with the transformer, then clipping with balanced series resistors and back-to-back diodes so the translator sees a higher dV/dT on its inputs. Might want to look in some old Motorola ECL appnotes for other possible schemes. Bob From: jimlux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wed, December 8, 2010 10:31:08 AM Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz -90dBc 10Hz -110dBc 100Hz -120dBc 1k-100k -125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Yes, and thus if you are going to use a comparator or line receiver (not recommended), then you should use the SLOWEST one that still works, if you want to optimize jitter. This is because the noise bandwidth is less. Bruce Griffiths wrote: One can estimate the resultant jitter from the input slew rate and the circuit noise and bandwidth. Too much bandwidth with a slow input slew rate increases the jitter substantially over that possible with an optimal circuit. Bruce Robert LaJeunesse wrote: Assuming a transformer coupled input (with biasing via a secondary center tap) why not use a fast differential PECL to CMOS level translator? For example, the IDT ICS508 will take 0.3 to 1.0 V p-p input and give 2.5, 3.3, or 5 V swing on the output. The chip works down to DC and keeps the duty cycle in the 40%-60% window up to 250MHz (at 3.3V out). Jitter and noise is not spec'd however. To increase the noise immunity with a relatively slow 10MHz sine source I'd look at boosting the amplitude with the transformer, then clipping with balanced series resistors and back-to-back diodes so the translator sees a higher dV/dT on its inputs. Might want to look in some old Motorola ECL appnotes for other possible schemes. Bob From: jimluxjim...@earthlink.net To: Discussion of precise time and frequency measurementtime-nuts@febo.com Sent: Wed, December 8, 2010 10:31:08 AM Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz-90dBc 10Hz-110dBc 100Hz-120dBc 1k-100k-125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
On 12/08/2010 06:28 PM, Rick Karlquist wrote: jimlux wrote: I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). In the 5071A at 80 MHz, we capacitively coupled a sine wave into a 74AC series logic gate, that had DC bias resistors to hold it at half the supply voltage. A feed-back resistor over an inverter and capacitive feed will self-bias such that PWM is 50%. The details of the gate being used may however prove lethal as you may end up with self-biasing into ring-modulation mode for some inverters being effectively three inverters in series. The use of a long-tailed pair on the input to gain out of the problem, prior to a gate for final squaring up would be my recommendation. It would be in the spirit of the Dick and Collins papers. The needed slew-rate gain will not be that great for 10 MHz to 100 MHz sine. You should not need to use very exotic setups to get the performance you need. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
On 12/08/2010 09:13 PM, Rick Karlquist wrote: Yes, and thus if you are going to use a comparator or line receiver (not recommended), then you should use the SLOWEST one that still works, if you want to optimize jitter. This is because the noise bandwidth is less. For optimum result you need to balance the slew-rate gain (essentially gain of the transition slew-rate) and the amount of added noise. You need a certain amount of bandwidth for a certain amount of output slew-rate, but higher bandwidth also gives more noise. A multi-stage setup use moderate gain and bandwidth in the initial stages, but it increases down the line. A few links: http://www.ko4bb.com/~bruce/CLKSHPR.html http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html As for transformer isolation, for most uses I find it fairly useless, but an RF-choke to isolate the front-end and the electronics RF-wise in common mode sense is more useful IMHO. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
I was thinking about how good or how bad would result the use of an LVDS line receiver ... but it is only a though :) Regards, Javier El 08/12/2010 19:50, Robert LaJeunesse escribió: Assuming a transformer coupled input (with biasing via a secondary center tap) why not use a fast differential PECL to CMOS level translator? For example, the IDT ICS508 will take 0.3 to 1.0 V p-p input and give 2.5, 3.3, or 5 V swing on the output. The chip works down to DC and keeps the duty cycle in the 40%-60% window up to 250MHz (at 3.3V out). Jitter and noise is not spec'd however. To increase the noise immunity with a relatively slow 10MHz sine source I'd look at boosting the amplitude with the transformer, then clipping with balanced series resistors and back-to-back diodes so the translator sees a higher dV/dT on its inputs. Might want to look in some old Motorola ECL appnotes for other possible schemes. Bob From: jimluxjim...@earthlink.net To: Discussion of precise time and frequency measurementtime-nuts@febo.com Sent: Wed, December 8, 2010 10:31:08 AM Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz-90dBc 10Hz-110dBc 100Hz-120dBc 1k-100k-125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. -- Javier HerreroEMAIL: jherr...@hvsistemas.com Chief Technology Officer HV Sistemas S.L. PHONE: +34 949 336 806 Los Charcones, 17 FAX: +34 949 336 792 19170 El Casar - Guadalajara - Spain WEB: http://www.hvsistemas.com ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
Of all the ways to square a sine wave I think the best might be to use a PLL. the raising edge of your output square wave would trigger a sample of the input sine wave. The distance from zero volts of that sample is the phase error. The goal is to have the raising edge of the square wave happen just as the sine crosses zero. But if it's not dead-on you get an error signal that can be either positive or negative and this error is low pass filtered and then applied as a correction. But my guess is that if you are using this to feed a 'scope a reference frequency the scope will have it's own PLL. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] reference oscillator input circuit
The Wenzel diff-amp circuit is OK but it will run out of steam before 100 MHz unless you use different transistors. On the other hand you really have to go out of your way to corrupt the signal at the -125 dBc/Hz level. At that level of play any decent comparator with the necessary slew rate will be fine. A 74AC gate looks good in this scenario: http://www.ke5fx.com/ac.htm ... subject to what other people have said about it being sensitive to input level. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of jimlux Sent: Wednesday, December 08, 2010 7:31 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] reference oscillator input circuit I'm looking for suggestions on a general circuit that can be used to receive an external frequency reference (nominally a real clean sine wave at, say, 10 MHz, although up to 100 MHz is possible) and turn it into a real clean square wave. Galvanic isolation is a plus (a transformer or capacitor would probably do that). I was thinking about rummaging through the schematics for test equipment reference inputs (since they've already solved the problem, eh?), but any other ideas would be welcome. I've scanned the archives of time-nuts, and while we have a fair amount of discussion on how to square up the 1Hz (or 100Hz) in a phase noise/ADEV setup, not so much on what to do with the 10 MHz. Rick has commented that you don't want to use a comparator. I have the papers by Dick, et al, and Collins, as well as all the others.. they tend to be looking at the low frequency problem, although the analysis is certainly applicable. I don't know that I'm looking for the whole multiple limiting stages scheme in any case. Oh, as far as performance.. Say the need is to not horribly degrade a good quality crystal oscillator... here's a typical set of specs: 76 MHz 1Hz -90dBc 10Hz -110dBc 100Hz -120dBc 1k-100k -125dBc Adevs of the oscillator run from 5E-12 at 0.1 sec, down to 1E-12 at 10 sec, and back up to 2 E-12 at 1000sec. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
