Rectify 500MHz Small Signal
in [Design]
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From: Jim Thompson on 26 Sep 2009 12:48 On Sat, 26 Sep 2009 09:37:49 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Sat, 26 Sep 2009 12:23:57 -0400, Phil Hobbs ><pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >>Jim Thompson wrote: >>> On Sat, 26 Sep 2009 11:09:43 GMT, nico(a)puntnl.niks (Nico Coesel) >>> wrote: >>> >>>> Bill Sloman <bill.sloman(a)ieee.org> wrote: >>>> >>>>> On Sep 25, 6:13=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >>>>> Web-Site.com> wrote: >>>>>> Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude >>>>>> say 50mV to 500mV peak-to-peak? >>>>>> >>>>>> Half wave is OK. >>>>>> >>>>>> 1mV accuracy is needed :-( >>>>>> >>>>>> Process is X-Fab XB06. >>>>> Barrie Gilbert has had some ideas. His AD834 >>>>> >>>>> http://www.analog.com/static/imported-files/data_sheets/AD834.pdf >>>>> >>>>> could be used to square your 500MHz signal, which automatically >>>>> rectifies it, though it leaves you with a lot of 1GHz ripple. >>>>> >>>>> If you wanted to do something cuter, you could phase-lock a nominally >>>>> 1GHz voltage-controlled logic level oscillator to the 500MHz signal, >>>>> and use it to generate two 500MHz signals mutually in quadrature - >>>>> nominally square waves, but at least with well-defined amplitudes, and >>>>> form in-phase and quadrature products. >>>>> >>>>> In a second order phase-locked loop, the quadrature output is >>>>> integrated to control the VCO such that the quadrature output is >>>>> precisely in quadrature with the incoming signal while the in-phase >>>>> output can be used to drive another product detector (aka multiplier) >>>>> whch gives you your rectified output. >>> >>> Of course, see my WVB receiver (on my website, SED page), dated 1974. >>> >>> Just ducky when you have ample headroom (�5V supplies). I have a >>> single supply, minimum operating at +2.7V >>> >>> And Gilbert cells aren't all that accurate without lots of voltage an >>> on-chip trimming... I need accuracy at small signals. >>> >>>> How about a s&h, a 7 bit ADC, peak hold register and a 6 bit DAC? >>> >>> Dream on ;-) >>> >>> ...Jim Thompson >> >>I like the electrical substitution idea already suggested (two diodes, >>drive one with DC to null out the signal from the other). How about >>ping-ponging a couple of them (say 75% duty cycle each), and measuring >>the offsets in between? You could measure the delta gain while they're >>both on (25% of the time) and the offsets when one or the other is off. >> With 75% duty cycle, they wouldn't ever be off together. >> >>Cheers >> >>Phil Hobbs > >There's the slideback technique: drive a comparator with RF on one >side, DC feedback on the other. Tease the DC appropriately. > >I once made a slideback sampling oscilloscope, using tunnel diodes, as >my EE senior project. I won an award and had to attend a dreadful IEEE >chapter banquet and repeat it to a bunch of old-fart power engineers >who didn't understand a word I said. I described the slideback >sampling scope in this ng some years back and a certain party loved >the idea so much he later decided that he'd invented it himself. > >HP used to sell a random sampling voltmeter. > >John John, Can you elaborate on your "slideback sampling"? Googling, I can find that you mentioned it, but no detail. I'm presently using a comparator scheme to find where the peak crosses a threshold. But as you can imagine, this is effectively PECL running at nearly 5GHz... giving me grief on the bias lines, plus lots of BS to get from positive-rail-referenced to ground-referenced... for a complex AGC loop that measures tank losses in a VCO (that's as far as I can go in explaining ;-) ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | LOSE the WUSS BRING BACK BUSH
From: Joerg on 26 Sep 2009 17:13 Vladimir Vassilevsky wrote: > > > John Larkin wrote: > >> On Fri, 25 Sep 2009 20:49:57 -0500, Vladimir Vassilevsky >> <nospam(a)nowhere.com> wrote: >> >> >>> >>> Tim Wescott wrote: >>> >>>> On Fri, 25 Sep 2009 09:13:53 -0700, Jim Thompson wrote: >>>> >>>>> Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude >>>>> say 50mV to 500mV peak-to-peak? >>>>> >>>>> Half wave is OK. >>>>> >>>>> 1mV accuracy is needed :-( >>>>> >>>> >>>> Make two identical paths, each with a diode, that lets you measure >>>> the DC current from the diode to ground. >>> >>> The 1mV accuracy requirement rules out the solutions with matched >>> diodes, not mentioning the unmatched ones. >> >> >> Everybody is doing this sort of thing these days: >> >> http://www.analog.com/en/rfif-components/log-ampsdetectors/ad8314/products/product.html >> We've done this sort of thing already in the early 90's :-) > > I thought about AD log detectors also, and Joerg suggested something > similar. However 1mV wrt 500mV = ~ 0.02dB; that's hardly feasible.If > such accuracy is really required, a solution could be a FET downmixer. > On a chip Jim has a ton of opportunities that us discrete designers don't have. Such as very good matching between neighboring components. Provided they are oriented in the same direction but that's easy. You can then run DC or an otherwise calibrated RF signal through a reference chain and error-correct the output. If the loop Jim needs doesn't have to be super-fast one could even servo. However, 1mV accuracy at 500mV is no small feat at 500MHz. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Joerg on 26 Sep 2009 17:19 Jim Thompson wrote: > On Sat, 26 Sep 2009 09:37:49 -0700, John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sat, 26 Sep 2009 12:23:57 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> Jim Thompson wrote: >>>> On Sat, 26 Sep 2009 11:09:43 GMT, nico(a)puntnl.niks (Nico Coesel) >>>> wrote: >>>> >>>>> Bill Sloman <bill.sloman(a)ieee.org> wrote: >>>>> >>>>>> On Sep 25, 6:13=A0pm, Jim Thompson <To-Email-Use-The-Envelope-I...(a)My- >>>>>> Web-Site.com> wrote: >>>>>>> Anyone have clever ideas for rectifying a 500MHz sine wave, amplitude >>>>>>> say 50mV to 500mV peak-to-peak? >>>>>>> >>>>>>> Half wave is OK. >>>>>>> >>>>>>> 1mV accuracy is needed :-( >>>>>>> >>>>>>> Process is X-Fab XB06. >>>>>> Barrie Gilbert has had some ideas. His AD834 >>>>>> >>>>>> http://www.analog.com/static/imported-files/data_sheets/AD834.pdf >>>>>> >>>>>> could be used to square your 500MHz signal, which automatically >>>>>> rectifies it, though it leaves you with a lot of 1GHz ripple. >>>>>> >>>>>> If you wanted to do something cuter, you could phase-lock a nominally >>>>>> 1GHz voltage-controlled logic level oscillator to the 500MHz signal, >>>>>> and use it to generate two 500MHz signals mutually in quadrature - >>>>>> nominally square waves, but at least with well-defined amplitudes, and >>>>>> form in-phase and quadrature products. >>>>>> >>>>>> In a second order phase-locked loop, the quadrature output is >>>>>> integrated to control the VCO such that the quadrature output is >>>>>> precisely in quadrature with the incoming signal while the in-phase >>>>>> output can be used to drive another product detector (aka multiplier) >>>>>> whch gives you your rectified output. >>>> Of course, see my WVB receiver (on my website, SED page), dated 1974. >>>> >>>> Just ducky when you have ample headroom (�5V supplies). I have a >>>> single supply, minimum operating at +2.7V >>>> >>>> And Gilbert cells aren't all that accurate without lots of voltage an >>>> on-chip trimming... I need accuracy at small signals. >>>> >>>>> How about a s&h, a 7 bit ADC, peak hold register and a 6 bit DAC? >>>> Dream on ;-) >>>> >>>> ...Jim Thompson >>> I like the electrical substitution idea already suggested (two diodes, >>> drive one with DC to null out the signal from the other). How about >>> ping-ponging a couple of them (say 75% duty cycle each), and measuring >>> the offsets in between? You could measure the delta gain while they're >>> both on (25% of the time) and the offsets when one or the other is off. >>> With 75% duty cycle, they wouldn't ever be off together. >>> >>> Cheers >>> >>> Phil Hobbs >> There's the slideback technique: drive a comparator with RF on one >> side, DC feedback on the other. Tease the DC appropriately. >> >> I once made a slideback sampling oscilloscope, using tunnel diodes, as >> my EE senior project. I won an award and had to attend a dreadful IEEE >> chapter banquet and repeat it to a bunch of old-fart power engineers >> who didn't understand a word I said. I described the slideback >> sampling scope in this ng some years back and a certain party loved >> the idea so much he later decided that he'd invented it himself. >> >> HP used to sell a random sampling voltmeter. >> >> John > > John, Can you elaborate on your "slideback sampling"? Googling, I can > find that you mentioned it, but no detail. > > I'm presently using a comparator scheme to find where the peak crosses > a threshold. > > But as you can imagine, this is effectively PECL running at nearly > 5GHz... giving me grief on the bias lines, plus lots of BS to get from > positive-rail-referenced to ground-referenced... for a complex AGC > loop that measures tank losses in a VCO (that's as far as I can go in > explaining ;-) > Ok, maybe I am totally off here now, but could you mix the VCO signal with a saturated (bang-bang) image of itself and also 90 deg of itself, then I/Q demodulate these two channels? That way you'd be close to DC, or to whatever loop speed you have. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Michael A. Terrell on 26 Sep 2009 17:28 John Larkin wrote: > > There's the slideback technique: drive a comparator with RF on one > side, DC feedback on the other. Tease the DC appropriately. > > I once made a slideback sampling oscilloscope, using tunnel diodes, as > my EE senior project. I won an award and had to attend a dreadful IEEE > chapter banquet and repeat it to a bunch of old-fart power engineers > who didn't understand a word I said. I described the slideback > sampling scope in this ng some years back and a certain party loved > the idea so much he later decided that he'd invented it himself. <http://store.americanmicrosemiconductor.com/diodes-tunnel-diodes.html> -- You can't have a sense of humor, if you have no sense!
From: John Larkin on 26 Sep 2009 19:52
On Sat, 26 Sep 2009 17:28:50 -0400, "Michael A. Terrell" <mike.terrell(a)earthlink.net> wrote: > >John Larkin wrote: >> >> There's the slideback technique: drive a comparator with RF on one >> side, DC feedback on the other. Tease the DC appropriately. >> >> I once made a slideback sampling oscilloscope, using tunnel diodes, as >> my EE senior project. I won an award and had to attend a dreadful IEEE >> chapter banquet and repeat it to a bunch of old-fart power engineers >> who didn't understand a word I said. I described the slideback >> sampling scope in this ng some years back and a certain party loved >> the idea so much he later decided that he'd invented it himself. > > ><http://store.americanmicrosemiconductor.com/diodes-tunnel-diodes.html> TDs are insanely expensive nowadays, ballpark $100. I used to get them for a couple bucks from Allied. The fabrication process is insane, and nobody ever modernized it. There are some more modern planar germanium back diodes, essentially low Ip tunnel diodes, but they're RF detectors, useless for switching. Pity, I used to like tunnel diodes. http://aeroflex.com/AMS/Metelics/pdfiles/MBD_Series_Planar_Back_Tunnel_Diodes.pdf John |