Rectify 500MHz Small Signal
in [Design]
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From: John Larkin on 26 Sep 2009 12:10 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 John
From: Phil Hobbs on 26 Sep 2009 12:23 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 -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: John Larkin on 26 Sep 2009 12:37 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
From: Vladimir Vassilevsky on 26 Sep 2009 12:38 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 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. Vladimir Vassilevsky DSP and Mixed Signal Design Consultant http://www.abvolt.com > John >
From: Jim Thompson on 26 Sep 2009 12:39
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 I'm sort of "ping-ponging" (diode current) to get chip (and external) temperatures. At 500MHz capacitance screws up rectification accuracy at low levels (BiCMOS process). ...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 |