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On Mon, 16 Feb 2004 21:02:02 GMT, James Meyer
wrote: On Mon, 16 Feb 2004 13:03:46 -0600, John Fields posted this: Starting with a perfect square wave at f1, bang the hell out of a diode with it, and then bandpass it and the 3rd harmonic (f2) separately, then mix them to get f1, f2, f1+f2, and f1-f2. Using a doubly balanced mixer will get rid of f1 and f2, then notching out f1+f2 will leave f1-f2, which will be 2f1, that non-existent second harmonic. What purpose does the diode serve? You're already starting with a "perfect" square wave. --- Duhhh.... None, of course. Thanks. -- John Fields |
In article , Paul Burridge wrote:
What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) Not radio, but interesting nevertheless. The older Hewlett-Packard cesium clocks, ie 5060/61/62 vintage multiplied a crystal oscillator up to 90 MHz in several stages. This fed into a step-recovery diode that sits in a cavity, and has 12.631... MHz applied to the SRD bias. The cavity selects the ***102nd*** harmonic ie 9180 MHz, and there are also sidebands at +/- 12.631.. MHz This is then fed into a hi-Q cavity tuned to the upper sideband ie 9192.631... MHz which is the desired cesium transition frequency. Adjusting the whole thing was a bit fiddly, and there were also some factory-set adjustments that you NEVER TOUCHED unless you had plenty of time and a squillion dollars worth of test gear. This was all a 1960's design and was a bit of a stretch. The newer (5071) clocks do things QUITE differently. Steve Quigg |
In article , Paul Burridge wrote:
What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) Not radio, but interesting nevertheless. The older Hewlett-Packard cesium clocks, ie 5060/61/62 vintage multiplied a crystal oscillator up to 90 MHz in several stages. This fed into a step-recovery diode that sits in a cavity, and has 12.631... MHz applied to the SRD bias. The cavity selects the ***102nd*** harmonic ie 9180 MHz, and there are also sidebands at +/- 12.631.. MHz This is then fed into a hi-Q cavity tuned to the upper sideband ie 9192.631... MHz which is the desired cesium transition frequency. Adjusting the whole thing was a bit fiddly, and there were also some factory-set adjustments that you NEVER TOUCHED unless you had plenty of time and a squillion dollars worth of test gear. This was all a 1960's design and was a bit of a stretch. The newer (5071) clocks do things QUITE differently. Steve Quigg |
Wadley loop recievers had to generate 33rd+ harmonic
Not quite OT but a great (old) idea http://www.siliconchip.com.au/cms/A_30512/article.html |
Wadley loop recievers had to generate 33rd+ harmonic
Not quite OT but a great (old) idea http://www.siliconchip.com.au/cms/A_30512/article.html |
I had a Yaesu FRG-7 receiver that used this lovely Wadley loop. If you
subscribe to the theory that every beep and bloop you hear as you tune across the dial is a station, that is the receiver for you! However, if you understand spurs and birdies, a different picture emerges. Lots of noise, too! "GPG" wrote in message om... Wadley loop recievers had to generate 33rd+ harmonic Not quite OT but a great (old) idea http://www.siliconchip.com.au/cms/A_30512/article.html |
I had a Yaesu FRG-7 receiver that used this lovely Wadley loop. If you
subscribe to the theory that every beep and bloop you hear as you tune across the dial is a station, that is the receiver for you! However, if you understand spurs and birdies, a different picture emerges. Lots of noise, too! "GPG" wrote in message om... Wadley loop recievers had to generate 33rd+ harmonic Not quite OT but a great (old) idea http://www.siliconchip.com.au/cms/A_30512/article.html |
Tell me how you will use that and I will tell you the answer.
"Paul Burridge" wrote in message ... What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) -- The BBC: Licensed at public expense to spread lies. |
Tell me how you will use that and I will tell you the answer.
"Paul Burridge" wrote in message ... What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) -- The BBC: Licensed at public expense to spread lies. |
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On Wed, 18 Feb 2004 10:05:58 GMT, Active8
,invalid wrote: Gee. I could have sworn Jim was hinting at the math approach. Wouldn'tcha just love to predict that roll-off on paper and *then* see it in real life? Starts with an "F", looks like a number, sounds like a frog. Fourier? I wouldn't trust it. Sounds French. :- -- The BBC: Licensed at public expense to spread lies. |
On Wed, 18 Feb 2004 10:05:58 GMT, Active8
,invalid wrote: Gee. I could have sworn Jim was hinting at the math approach. Wouldn'tcha just love to predict that roll-off on paper and *then* see it in real life? Starts with an "F", looks like a number, sounds like a frog. Fourier? I wouldn't trust it. Sounds French. :- -- The BBC: Licensed at public expense to spread lies. |
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In article ,
Paul Burridge wrote: What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) Depends on what you call "practical". I know that one type of atomic clock uses a one stage frequency multiplier to go from about 10MHz to about 9.1GHz. A slow edged square wave follows the 1/N rule to about the point where the rise or fall time is equal to half a cycle of the harmonic frequency. From that point up, the spectrum falls off at a rate of at least 1/n^2. Usually it is faster than that. If we assume that the 5nS rise time is the input to a stage, we can use a fast transistor to effectively speed the edge up. -- -- forging knowledge |
In article ,
Paul Burridge wrote: What's the maximum multiplication factor it's practical and sensible to attempt to achieve in one single stage of multiplication? (Say from a 7Mhz square wave source with 5nS rise/fall times.) Depends on what you call "practical". I know that one type of atomic clock uses a one stage frequency multiplier to go from about 10MHz to about 9.1GHz. A slow edged square wave follows the 1/N rule to about the point where the rise or fall time is equal to half a cycle of the harmonic frequency. From that point up, the spectrum falls off at a rate of at least 1/n^2. Usually it is faster than that. If we assume that the 5nS rise time is the input to a stage, we can use a fast transistor to effectively speed the edge up. -- -- forging knowledge |
Avery Fineman wrote:
. . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. Roy Lewallen, W7EL |
Avery Fineman wrote:
. . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. Roy Lewallen, W7EL |
In article , Roy Lewallen
writes: Avery Fineman wrote: . . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Okay. I can't agree that they are "easy" after having enough occasions to make several. :-) Your mileage, of course, varies. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave from either another multiplier or an oscillator. Rocket science it ain't. BREADBOARD. A most handy part of the bench tools. Recommended first. Especially for those purist hobbyists who think that digital circuits aren't "real radio." :-) Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person |
In article , Roy Lewallen
writes: Avery Fineman wrote: . . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Okay. I can't agree that they are "easy" after having enough occasions to make several. :-) Your mileage, of course, varies. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave from either another multiplier or an oscillator. Rocket science it ain't. BREADBOARD. A most handy part of the bench tools. Recommended first. Especially for those purist hobbyists who think that digital circuits aren't "real radio." :-) Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person |
In article , Roy Lewallen
writes: Avery Fineman wrote: . . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Okay. I can't agree that they are "easy" after having enough occasions to make several. :-) Your mileage, of course, varies. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave from either another multiplier or an oscillator. Rocket science it ain't. BREADBOARD. A most handy part of the bench tools. Recommended first. Especially for those purist hobbyists who think that digital circuits aren't "real radio." :-) Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person |
In article , Roy Lewallen
writes: Avery Fineman wrote: . . . Making practical, reproducible active multipliers in the home shop is, practically, a trial-and-error process involving playing with cut- off bias of the active device input, energy and harmonic content of the source, and Q of the multiplier's output stage. In the past I've made tripling-in-the-plate pentode crystal oscillators using fundamental frequency quartz but those were highly dependent on getting the highest impedance tuned plate circuit and needed scope viewing to check output waveforms. Not very reproducible. There's no "easy" way to do it that will "work every time" despite the claims of many. :-) . . . While that's certainly true of multipliers in general, I've certainly found it very easy to make repeatable doublers with a two transistor push-push stage. Driving it with about zero bias and a large enough signal to get it to conduct on at least a good fraction of each cycle gives plenty of harmonic energy. A collector circuit with decent Q will take care of most higher harmonics, although a simple filter following the stage is usually adequate for more demanding applications. The fundamental can be nulled out reasonably well with a pot between emitters with a grounded center tap. I'd think a push-pull tripler would be nearly as easy, but I haven't had occasion to make one. Okay. I can't agree that they are "easy" after having enough occasions to make several. :-) Your mileage, of course, varies. Several simple diode and transistor multipliers are described in Chapter 5 of _Experimental Methods in RF Design_, which I heartily recommend for the homebrewer and experimenter. A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave from either another multiplier or an oscillator. Rocket science it ain't. BREADBOARD. A most handy part of the bench tools. Recommended first. Especially for those purist hobbyists who think that digital circuits aren't "real radio." :-) Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person |
Avery Fineman wrote:
. . . Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person Yes, that book is published by the ARRL. Its authors, Wes Hayward, W7ZOI; Rick Campbell, KK7B; and Bob Larkin, W7PUA have, unlike so many authors, spent careers doing just what you and I have had to do -- produce hardware results. Of them, I know Wes the best, having been friends with him for about 30 years. After a stint at Boeing long ago, Wes was a design engineer in the spectrum analyzer group at Tektronix for a number of years, where his designs were incorporated in a number of state-of-the-art spectrum analyzers. He went from there to TriQuint semiconductor, where he designed many RF components which are in daily use in probably millions of cell phones and other wireless products. He recently retired and has been doing some consulting. His publications in amateur journals, spanning decades, are legendary and many are seminal. I don't know Rick quite as well, but he's also a very capable and accomplished engineer (in spite, one might say, of his Ph.D. and period in academia). For years now, he's also worked as a design engineer at TriQuint. To get a feel for his approach to solving real problems, check out the articles he's published over the years in QST on phasing type direct conversion receivers. Bob I don't know at all, but Wes speaks very highly of him, and I have absolute confidence in Wes' judgement of skill. There's nothing in that book that hasn't been built and tested, and designed to be repeatable. And everything has been designed by people who really know what they're doing. This isn't a book of kluged-it-up-on-the-bench-and-made-one-work-once projects as so many are. I'm sure that if you'd take a few minutes to look over the book, you'd immediately recognize that. To answer your specific question, I don't, in a brief scan, see details in the book about optimizing the bias for maximum harmonic content of the multipliers. Most are diode multipliers anyway, with no bias adjustment. The book covers a very wide range of topics, and the section on multipliers consists of only a couple of pages of text. There is, however, a chapter on simple test equipment a homebrewer can build, including a brief description of a practical spectrum analyzer. Wes did, incidentally, design and publish such a thing some years ago. I think it's still available in kit form from Kanga US. I've also spent a career having to produce real results. But apparently our approaches differed, because I've found that good paper designs, often aided by fundamental knowledge gleaned from books, lead to good hardware results, rather than being an opposing and somehow inferior method. And they have the advantage of being well understood, predictable, and repeatable. Roy Lewallen, W7EL |
Avery Fineman wrote:
. . . Playing with bias on a transistor multiplier stage is fine for optimizing a multiplication but all it is is play when there's nothing to compare one bias setting with another as to power output at the desired multiple. A spectrum analyzer isn't an absolute need, by the way, there's other ways to measure the harmonic content. Is that in "Experimental Methods..." published by the ARRL? [I'm pushing work-on-the-bench, not books, pardon my attitude that has resulted from years of having to produce hardware results, not paper reports] Len Anderson retired (from regular hours) electronic engineering person Yes, that book is published by the ARRL. Its authors, Wes Hayward, W7ZOI; Rick Campbell, KK7B; and Bob Larkin, W7PUA have, unlike so many authors, spent careers doing just what you and I have had to do -- produce hardware results. Of them, I know Wes the best, having been friends with him for about 30 years. After a stint at Boeing long ago, Wes was a design engineer in the spectrum analyzer group at Tektronix for a number of years, where his designs were incorporated in a number of state-of-the-art spectrum analyzers. He went from there to TriQuint semiconductor, where he designed many RF components which are in daily use in probably millions of cell phones and other wireless products. He recently retired and has been doing some consulting. His publications in amateur journals, spanning decades, are legendary and many are seminal. I don't know Rick quite as well, but he's also a very capable and accomplished engineer (in spite, one might say, of his Ph.D. and period in academia). For years now, he's also worked as a design engineer at TriQuint. To get a feel for his approach to solving real problems, check out the articles he's published over the years in QST on phasing type direct conversion receivers. Bob I don't know at all, but Wes speaks very highly of him, and I have absolute confidence in Wes' judgement of skill. There's nothing in that book that hasn't been built and tested, and designed to be repeatable. And everything has been designed by people who really know what they're doing. This isn't a book of kluged-it-up-on-the-bench-and-made-one-work-once projects as so many are. I'm sure that if you'd take a few minutes to look over the book, you'd immediately recognize that. To answer your specific question, I don't, in a brief scan, see details in the book about optimizing the bias for maximum harmonic content of the multipliers. Most are diode multipliers anyway, with no bias adjustment. The book covers a very wide range of topics, and the section on multipliers consists of only a couple of pages of text. There is, however, a chapter on simple test equipment a homebrewer can build, including a brief description of a practical spectrum analyzer. Wes did, incidentally, design and publish such a thing some years ago. I think it's still available in kit form from Kanga US. I've also spent a career having to produce real results. But apparently our approaches differed, because I've found that good paper designs, often aided by fundamental knowledge gleaned from books, lead to good hardware results, rather than being an opposing and somehow inferior method. And they have the advantage of being well understood, predictable, and repeatable. Roy Lewallen, W7EL |
Roy Lewallen wrote in message ...
... I've found that good paper designs, often aided by fundamental knowledge gleaned from books, lead to good hardware results, rather than being an opposing and somehow inferior method. And they have the advantage of being well understood, predictable, and repeatable. Indeed. Occasionaly new not-yet-understood phenomena are discovered on the bench, but the art benefits greatly from a detailed understanding of the underlying mechanisms. Coincidently, I was browsing "Inventions of Opportunity" this afternoon and stumbled across an article about how in the late 1950's a newly-developed high speed sampling scope aided in understanding harmonic-generation mechanisms in diodes, which apparently helped a lot in the development of step recovery diodes. Before that, apparently there wasn't good understanding about why some diodes generated lots of harmonics and others didn't. Step recovery diodes are optimized for fast turn-off of the reverse recovery, and are used in generating a "comb" of harmonics. It's not uncommon to pick off the desired harmonic with an appropriate filter, up to beyond the tenth harmonic. Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. With a little understanding of the spectrum of a non-symmetrical square (or trapezoid) wave, it's not hard to come very close to an optimum bias and drive for a given harmonic output in an amplifier stage. If you do it just by experimentation, you're liable to find a local optimum that's quite a bit worse than the global optimum. Same with the output coupling/filtering network. Cheers, Tom |
Roy Lewallen wrote in message ...
... I've found that good paper designs, often aided by fundamental knowledge gleaned from books, lead to good hardware results, rather than being an opposing and somehow inferior method. And they have the advantage of being well understood, predictable, and repeatable. Indeed. Occasionaly new not-yet-understood phenomena are discovered on the bench, but the art benefits greatly from a detailed understanding of the underlying mechanisms. Coincidently, I was browsing "Inventions of Opportunity" this afternoon and stumbled across an article about how in the late 1950's a newly-developed high speed sampling scope aided in understanding harmonic-generation mechanisms in diodes, which apparently helped a lot in the development of step recovery diodes. Before that, apparently there wasn't good understanding about why some diodes generated lots of harmonics and others didn't. Step recovery diodes are optimized for fast turn-off of the reverse recovery, and are used in generating a "comb" of harmonics. It's not uncommon to pick off the desired harmonic with an appropriate filter, up to beyond the tenth harmonic. Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. With a little understanding of the spectrum of a non-symmetrical square (or trapezoid) wave, it's not hard to come very close to an optimum bias and drive for a given harmonic output in an amplifier stage. If you do it just by experimentation, you're liable to find a local optimum that's quite a bit worse than the global optimum. Same with the output coupling/filtering network. Cheers, Tom |
Tom Bruhns wrote:
. . . . . . Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. . . . Getting a bit off-topic here, but as of a few years ago, we were using step recovery diodes to generate the step in high speed TDR systems, and to generate the strobe for the sampling gate in high speed sampling scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50 GHz or so), limited primarily by circuitry external to the diodes. SRDs replaced tunnel diodes in earlier generations of instruments. I've been out of touch with that class of instruments for a few years now -- do you know if something has replaced the SRD for generating fast steps, or just for harmonic generation? Roy Lewallen, W7EL |
Tom Bruhns wrote:
. . . . . . Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. . . . Getting a bit off-topic here, but as of a few years ago, we were using step recovery diodes to generate the step in high speed TDR systems, and to generate the strobe for the sampling gate in high speed sampling scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50 GHz or so), limited primarily by circuitry external to the diodes. SRDs replaced tunnel diodes in earlier generations of instruments. I've been out of touch with that class of instruments for a few years now -- do you know if something has replaced the SRD for generating fast steps, or just for harmonic generation? Roy Lewallen, W7EL |
On Sat, 21 Feb 2004 03:20:07 -0800, Roy Lewallen
wrote: Tom Bruhns wrote: . . . . . . Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. . . . Getting a bit off-topic here, but as of a few years ago, we were using step recovery diodes to generate the step in high speed TDR systems, and to generate the strobe for the sampling gate in high speed sampling scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50 GHz or so), limited primarily by circuitry external to the diodes. SRDs replaced tunnel diodes in earlier generations of instruments. I've been out of touch with that class of instruments for a few years now -- do you know if something has replaced the SRD for generating fast steps, or just for harmonic generation? What's a doubler based on the good old 1N4148 good for, top end frequency-wise? -- The BBC: Licensed at public expense to spread lies. |
On Sat, 21 Feb 2004 03:20:07 -0800, Roy Lewallen
wrote: Tom Bruhns wrote: . . . . . . Seems like step recovery diodes are not in as great favor as they once were, since there are generally better ways to generate higher order harmonics. . . . Getting a bit off-topic here, but as of a few years ago, we were using step recovery diodes to generate the step in high speed TDR systems, and to generate the strobe for the sampling gate in high speed sampling scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50 GHz or so), limited primarily by circuitry external to the diodes. SRDs replaced tunnel diodes in earlier generations of instruments. I've been out of touch with that class of instruments for a few years now -- do you know if something has replaced the SRD for generating fast steps, or just for harmonic generation? What's a doubler based on the good old 1N4148 good for, top end frequency-wise? -- The BBC: Licensed at public expense to spread lies. |
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In article , Paul Burridge
writes: On 20 Feb 2004 21:53:26 GMT, (Avery Fineman) wrote: A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave Is the type of distortion critical? How about a clipped/clamped sinewave? Yes and no. :-) A quantitative answer isn't possible since the waveform must be described accurately in shape (or spectrum analyzed) in order to determine the harmonic content. Suffice to say that a square wave cannot be used with a passive diode doubler; all the energy is contained in the short transition times and that is rarely enough to be worth it. If an untuned oscillator output is to be doubled, that scoped waveform will quite probably look distorted. Such is quite likely to be a good harmonic content source for a passive diode doubler. The obvious alternate is to tune the oscillator output to the second (or third) harmonic right off... :-) I mentioned diode doublers because (1) they are passive; (2) they are relatively broadband; (3) common legacy fast diodes such as 1N914 and 1N4148 can work in that application beyond 20 MHz; (4) they work with cylindrical-shape coils also but toroidals forms make the whole circuit physically smaller. If the source's impedance is too high to handle a passive diode multiplier, then an active-device multiplier is a better choice. [at this point it is a promotional insert time to publicize ARRL publications of "tried and proven circuits" provided one copies ALL the parts of the circuit exactly as shown to be tried and proven...:-) ] The original thread question was general enough that the number of variables would fill a shopping cart. Quantitative answers to such questions aren't possible. At best, only suggestions of a general nature can be the answers. Digital logic off-the-shelf is excellent for making things right off the paper design because they work with two stable states with very high transition times; stay within the rise, fall, and propagation times and fan-out rules and it should work right off the scratchpad. Analog circuits are a whole new game with different rules and a large number of unknowns even if some detailed specs are available. For one-of-a-kind homebrew applications of analog multipliers, I'd say it was time for experimental bench cut-and-try work first. A paper analysis is going to take TIME even if the smarts are there. Empirical data derivation (cut-and-try) is quick, much quicker than the paper chase. I say empirical since the supply voltages may be different than some book example, few have instruments for measuring source and load impedances or spectral content and power level of the source. The simpler the prototype-idea circuit, the easier it is to make a stock kind of circuit on the bench and probably characterize it over a wide frequency range and, possibly, with varying supply rail voltages and power levels. Heh...a LOT of production circuits were engineered that way even though the companies who made it came along after and made them look like seven wonders of the world in PR literature later. They were after _reproducible_ circuits in _their_ systems, not as shining textbook examples. Some passive component values may have been selected to reduce the overall type-of-parts count by using "common" values needed in other circuits. That's perfectly acceptible as long as a circuit works and can be reproduced...at a profit. :-) Can I answer your original question? Not really. Think of a passive diode doubler as a full-wave rectifier. Those take a fundamental sine and "double it over" (negative swing made positive through trans- former) to make two half-sine pulses of the same polarity for each full AC cycle. There's a lot of "second harmonic" in that rectifier output...which makes for easier filtering since the ripple voltage frequency is twice what it would be for a half-wave rectifier. Using fast legacy diodes at a much higher frequency turns out to be the same sort of thing. Unlike a rectifier circuit, the output of the doubler can be tuned to that second harmonic (a no-no for most power supply rectifiers) to get the most output. You could use a clipped sinewave input, but why and where is the clipping done and what extra circuits or components are needed to justify that? I've only outlined SOME of the mental questions each brewer has to make for themselves. Concentration is needed for application. Len Anderson retired (from regular hours) electronic engineer person |
In article , Paul Burridge
writes: On 20 Feb 2004 21:53:26 GMT, (Avery Fineman) wrote: A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave Is the type of distortion critical? How about a clipped/clamped sinewave? Yes and no. :-) A quantitative answer isn't possible since the waveform must be described accurately in shape (or spectrum analyzed) in order to determine the harmonic content. Suffice to say that a square wave cannot be used with a passive diode doubler; all the energy is contained in the short transition times and that is rarely enough to be worth it. If an untuned oscillator output is to be doubled, that scoped waveform will quite probably look distorted. Such is quite likely to be a good harmonic content source for a passive diode doubler. The obvious alternate is to tune the oscillator output to the second (or third) harmonic right off... :-) I mentioned diode doublers because (1) they are passive; (2) they are relatively broadband; (3) common legacy fast diodes such as 1N914 and 1N4148 can work in that application beyond 20 MHz; (4) they work with cylindrical-shape coils also but toroidals forms make the whole circuit physically smaller. If the source's impedance is too high to handle a passive diode multiplier, then an active-device multiplier is a better choice. [at this point it is a promotional insert time to publicize ARRL publications of "tried and proven circuits" provided one copies ALL the parts of the circuit exactly as shown to be tried and proven...:-) ] The original thread question was general enough that the number of variables would fill a shopping cart. Quantitative answers to such questions aren't possible. At best, only suggestions of a general nature can be the answers. Digital logic off-the-shelf is excellent for making things right off the paper design because they work with two stable states with very high transition times; stay within the rise, fall, and propagation times and fan-out rules and it should work right off the scratchpad. Analog circuits are a whole new game with different rules and a large number of unknowns even if some detailed specs are available. For one-of-a-kind homebrew applications of analog multipliers, I'd say it was time for experimental bench cut-and-try work first. A paper analysis is going to take TIME even if the smarts are there. Empirical data derivation (cut-and-try) is quick, much quicker than the paper chase. I say empirical since the supply voltages may be different than some book example, few have instruments for measuring source and load impedances or spectral content and power level of the source. The simpler the prototype-idea circuit, the easier it is to make a stock kind of circuit on the bench and probably characterize it over a wide frequency range and, possibly, with varying supply rail voltages and power levels. Heh...a LOT of production circuits were engineered that way even though the companies who made it came along after and made them look like seven wonders of the world in PR literature later. They were after _reproducible_ circuits in _their_ systems, not as shining textbook examples. Some passive component values may have been selected to reduce the overall type-of-parts count by using "common" values needed in other circuits. That's perfectly acceptible as long as a circuit works and can be reproduced...at a profit. :-) Can I answer your original question? Not really. Think of a passive diode doubler as a full-wave rectifier. Those take a fundamental sine and "double it over" (negative swing made positive through trans- former) to make two half-sine pulses of the same polarity for each full AC cycle. There's a lot of "second harmonic" in that rectifier output...which makes for easier filtering since the ripple voltage frequency is twice what it would be for a half-wave rectifier. Using fast legacy diodes at a much higher frequency turns out to be the same sort of thing. Unlike a rectifier circuit, the output of the doubler can be tuned to that second harmonic (a no-no for most power supply rectifiers) to get the most output. You could use a clipped sinewave input, but why and where is the clipping done and what extra circuits or components are needed to justify that? I've only outlined SOME of the mental questions each brewer has to make for themselves. Concentration is needed for application. Len Anderson retired (from regular hours) electronic engineer person |
On 21 Feb 2004 19:47:23 GMT, (Avery Fineman)
wrote: In article , Paul Burridge writes: On 20 Feb 2004 21:53:26 GMT, (Avery Fineman) wrote: A diode doubler using a toroid transformer, pair of diodes and a tuned circuit in the output works fine right off the paper pad and slide-rule (or calculator) numbers. Typically the source is a distorted sinewave Is the type of distortion critical? How about a clipped/clamped sinewave? Yes and no. :-) A quantitative answer isn't possible since the waveform must be described accurately in shape (or spectrum analyzed) in order to determine the harmonic content. Suffice to say that a square wave cannot be used with a passive diode doubler; all the energy is contained in the short transition times and that is rarely enough to be worth it. [snip...] Thanks, Len. A lot of good stuff to be considered here so I'll save it for now and go through it later..... p. -- The BBC: Licensed at public expense to spread lies. |
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"Tom Bruhns" Wrote:
(Avery Fineman) wrote in message ... ... Suffice to say that a square wave cannot be used with a passive diode doubler; all the energy is contained in the short transition times and that is rarely enough to be worth it. ?? Lots of energy in the fundamental; filter to extract the fundamental and feed it to your full-wave rectifier doubler. Efficiency can be high if the filter does not cause dissipation in the source at the harmonics. Tom, look at it this way... Draw the square wave, assuming capacitive coupling so it has a zero crossing. Then draw the same signal but invert the negative going half to positive, which is what the full wave diode doubler would do. You wind up with a positive voltage, but with VERY narrow negative spikes. So, a square wave into a diode doubler will produce only a small amount of the second harmonic. You'd be better off running the input square wave through a lowpass of some sort and then doubling it. Given a sine wave input, there is a fair amount of negative going signal and that is what produces the high energy content of the second harmonic. Jim Pennell N6BIU |
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