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On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
Frequency multiplication
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. |
I think it boils down to something very practical:
If you want good spectral purity, then you need to bandpass filter the output of the multiplier. It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. After that, you can consult your filter design charts to determine how complex a filter will be required and whether it's physically realizable. As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. This means the output bandpass filter has to be able to attenuate signals at +/-25% of the center frequency sufficiently to meet the desired spectral purity. In practice with simple single-ended multiplier designs, a x4 multiplier is approaching the threshold of realizability for high purity applications (40-60 dB purity). It is possible to make push-pull and push-push multipliers that have better output purity, but these techniques are seldom used. Joe W3JDR "Jim Thompson" wrote in message ... On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
I think it boils down to something very practical:
If you want good spectral purity, then you need to bandpass filter the output of the multiplier. It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. After that, you can consult your filter design charts to determine how complex a filter will be required and whether it's physically realizable. As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. This means the output bandpass filter has to be able to attenuate signals at +/-25% of the center frequency sufficiently to meet the desired spectral purity. In practice with simple single-ended multiplier designs, a x4 multiplier is approaching the threshold of realizability for high purity applications (40-60 dB purity). It is possible to make push-pull and push-push multipliers that have better output purity, but these techniques are seldom used. Joe W3JDR "Jim Thompson" wrote in message ... On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:
I think it boils down to something very practical: If you want good spectral purity, then you need to bandpass filter the output of the multiplier. It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. After that, you can consult your filter design charts to determine how complex a filter will be required and whether it's physically realizable. As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. This means the output bandpass filter has to be able to attenuate signals at +/-25% of the center frequency sufficiently to meet the desired spectral purity. In practice with simple single-ended multiplier designs, a x4 multiplier is approaching the threshold of realizability for high purity applications (40-60 dB purity). It is possible to make push-pull and push-push multipliers that have better output purity, but these techniques are seldom used. Joe W3JDR [snip] I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:
I think it boils down to something very practical: If you want good spectral purity, then you need to bandpass filter the output of the multiplier. It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. After that, you can consult your filter design charts to determine how complex a filter will be required and whether it's physically realizable. As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. This means the output bandpass filter has to be able to attenuate signals at +/-25% of the center frequency sufficiently to meet the desired spectral purity. In practice with simple single-ended multiplier designs, a x4 multiplier is approaching the threshold of realizability for high purity applications (40-60 dB purity). It is possible to make push-pull and push-push multipliers that have better output purity, but these techniques are seldom used. Joe W3JDR [snip] I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
On Sun, 15 Feb 2004 23:48:47 +0000, 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.) While you might be able to generate odd harmonics of a 1 kHz square wave up to several hundred megahertz, there are two practical problems. First you would need some method to separate the wanted harmonic from the unwanted. For low multiplication factors in HF/VHF a series of bandpass LC filters would be needed to attenuate the unwanted harmonics. For higher frequencies some helical or cavity resonators may be needed. One old method to separate nearby harmonics is to use a wave analyser. The wanted harmonics is mixed down with a VFO to some fixed intermediate frequency in which a fixed crystal filter is inserted (bandwidth 0,5-50 kHz depending on application). The filtered and amplified signal is then mixed back to the original frequency by the same VFO. The absolute stability of the VFO does not matter very much, since any drift is cancelled in the up-conversion. However, the stability must be sufficient to keep the desired harmonics within the IF filter bandwidth. This kind of tricks was once used to multiply some high precision frequency standard to some odd (say 61th harmonic). The other problem with high multiplication factors is that the amplitude of the higher harmonics is quite low, thus needing quite a lot of amplification after filtering. However, the level of the original harmonics was low compared also to the wide band thermal (white) noise, thus, after amplification, the wide band thermal noise level is also high, reducing the final signal to noise ratio and in reception, cause reciprocal mixing programs. Thus, it is better to use several multiplier stages with low multiplication factors, since it easier to filter out the desired harmonics after each multiplier. The gain distribution is also better, thus the noise floor does not become uncomfortably close to the wanted signal. However, if some strange multiplication factor (such as the 17th) is needed (in which case a series of multipliers can not be used), these days it would be easier to use a PLL with a fixed digital divider. Keep the VCO tuning range as small as possible, thus reducing the MHz/V sensitivity and noise through the tuning line and use a large loop bandwidth to clean the areas around the generated signal. Paul OH3LWR |
On Sun, 15 Feb 2004 23:48:47 +0000, 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.) While you might be able to generate odd harmonics of a 1 kHz square wave up to several hundred megahertz, there are two practical problems. First you would need some method to separate the wanted harmonic from the unwanted. For low multiplication factors in HF/VHF a series of bandpass LC filters would be needed to attenuate the unwanted harmonics. For higher frequencies some helical or cavity resonators may be needed. One old method to separate nearby harmonics is to use a wave analyser. The wanted harmonics is mixed down with a VFO to some fixed intermediate frequency in which a fixed crystal filter is inserted (bandwidth 0,5-50 kHz depending on application). The filtered and amplified signal is then mixed back to the original frequency by the same VFO. The absolute stability of the VFO does not matter very much, since any drift is cancelled in the up-conversion. However, the stability must be sufficient to keep the desired harmonics within the IF filter bandwidth. This kind of tricks was once used to multiply some high precision frequency standard to some odd (say 61th harmonic). The other problem with high multiplication factors is that the amplitude of the higher harmonics is quite low, thus needing quite a lot of amplification after filtering. However, the level of the original harmonics was low compared also to the wide band thermal (white) noise, thus, after amplification, the wide band thermal noise level is also high, reducing the final signal to noise ratio and in reception, cause reciprocal mixing programs. Thus, it is better to use several multiplier stages with low multiplication factors, since it easier to filter out the desired harmonics after each multiplier. The gain distribution is also better, thus the noise floor does not become uncomfortably close to the wanted signal. However, if some strange multiplication factor (such as the 17th) is needed (in which case a series of multipliers can not be used), these days it would be easier to use a PLL with a fixed digital divider. Keep the VCO tuning range as small as possible, thus reducing the MHz/V sensitivity and noise through the tuning line and use a large loop bandwidth to clean the areas around the generated signal. Paul OH3LWR |
On Sun, 15 Feb 2004 16:46:32 -0700, Jim Thompson
wrote: On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? I suppose it boils down to how much signal is left in the mush as the harmonics get higher and higher. Knew I shoulda held on to that spectrum analyser I used to have. :-( I suppose that's the proper answer though: get the rise/fall times as small and possible, measure the specral output and pick a suitable harmonic with enough energy in it to set it 'comfortably' above the noise floor? -- The BBC: Licensed at public expense to spread lies. |
On Sun, 15 Feb 2004 16:46:32 -0700, Jim Thompson
wrote: On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? I suppose it boils down to how much signal is left in the mush as the harmonics get higher and higher. Knew I shoulda held on to that spectrum analyser I used to have. :-( I suppose that's the proper answer though: get the rise/fall times as small and possible, measure the specral output and pick a suitable harmonic with enough energy in it to set it 'comfortably' above the noise floor? -- The BBC: Licensed at public expense to spread lies. |
"Jim Thompson" wrote in message ... On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | One would think a "PE" could give the man a civil answer. Pete |
"Jim Thompson" wrote in message ... On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | One would think a "PE" could give the man a civil answer. Pete |
I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers. I guessed I missed Jim's comment in the earlier post, or I would have replied earlier. Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it. Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage. In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined. Joe W3JDR |
I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers. I guessed I missed Jim's comment in the earlier post, or I would have replied earlier. Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it. Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage. In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined. Joe W3JDR |
On Mon, 16 Feb 2004 17:02:20 GMT, "W3JDR" wrote:
I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. I guessed I missed Jim's comment in the earlier post, or I would have replied earlier. Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it. Only mildly so, just "funning" you ;-) Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage. In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined. Joe W3JDR It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
On Mon, 16 Feb 2004 17:02:20 GMT, "W3JDR" wrote:
I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. I guessed I missed Jim's comment in the earlier post, or I would have replied earlier. Jim, I'm not not sure what you're trying to say, but there seems to be a sarcastic undertone to the way you said it. Only mildly so, just "funning" you ;-) Anyway, it turns out that non-linear single-ended elements are great generators of even-order harmonics. That's why the classical HF/VHF multiplier circuit is typically a single ended transistor amplifier with output and input tuned to different frequencies. If you bias the device so it is non-linear, then it becomes a natural harmonic generator. You can enhance even-order generation and supress the odd-order generation by using a non-linear 'push-push' stage, just as you can suppress even order harmonics with a 'push-pull' stage. In either case, the important thing to remember is that symmetrical clipping or limiting generates mostly odd-order distortion and unsymmetrical clipping or limiting generates mostly even order distortion. The quantification of this is left to those more mathematically inclined. Joe W3JDR It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. ...Jim Thompson -- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |
It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. Oh! I see what you're talking about... I presumed that he was starting with a single spectral component (sine wave) and wanted to end up with another single spectral component. Joe W3JDR |
It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. Oh! I see what you're talking about... I presumed that he was starting with a single spectral component (sine wave) and wanted to end up with another single spectral component. Joe W3JDR |
On Mon, 16 Feb 2004 11:40:18 -0500, " Uncle Peter"
wrote: "Jim Thompson" wrote in message .. . On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | One would think a "PE" could give the man a civil answer. --- Jim's not a civil engineer... -- John Fields |
On Mon, 16 Feb 2004 11:40:18 -0500, " Uncle Peter"
wrote: "Jim Thompson" wrote in message .. . On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson -- | James E.Thompson, P.E. | mens | One would think a "PE" could give the man a civil answer. --- Jim's not a civil engineer... -- John Fields |
Not really, Jim...unless you mean something special by "nonlinear
multipliers" like diodes/varactors which I suspect fall under your comment. In the two-way radios of the 60's & early 80's before synthesizers, I designed many a single stage multiplier of 2x or 3x, which were preferred and sometimes 4x. They worked very well...using cap input coupling, to keep the base Z low at the harmonics and keeping the conduction angle optimized for output level. Also, the adjacent harmonics are easier to filter than higher orders of multiplication (when that is a factor. Only a single resonant circuit was required between stages. The bottom line depends upon the spurious requirements. Then there are always preferences for what we may have used in the past - and what the application actually is. Starting with a spectral comb(like a square wave or other pulse-type waveform) and picking off the desired harmonic can also be very effective, but again, it depends upon the specific application. I did a synthesizer mixer with no tuned circuits to get from 40 MHz crystal oscillator to 220MHz to mix down a VCO to an IF for the programmable divider. Was really sweet! Did the same for what I believe was the very first synthesized 2M hand held in 1973. A Motorola HT220. Even had the Transmit VCO _ON_ yes _ON_ the TX frequency. Total current drain was 7ma. Tx spurious (-70dBc) better than the original (-35-40dB) Still have it. -- Steve N, K,9;d, c. i My email has no u's. "Jim Thompson" wrote in message ... On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I think it boils down to something very practical: ...It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. ... As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. ... Joe, W3JDR [snip] I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson |
Not really, Jim...unless you mean something special by "nonlinear
multipliers" like diodes/varactors which I suspect fall under your comment. In the two-way radios of the 60's & early 80's before synthesizers, I designed many a single stage multiplier of 2x or 3x, which were preferred and sometimes 4x. They worked very well...using cap input coupling, to keep the base Z low at the harmonics and keeping the conduction angle optimized for output level. Also, the adjacent harmonics are easier to filter than higher orders of multiplication (when that is a factor. Only a single resonant circuit was required between stages. The bottom line depends upon the spurious requirements. Then there are always preferences for what we may have used in the past - and what the application actually is. Starting with a spectral comb(like a square wave or other pulse-type waveform) and picking off the desired harmonic can also be very effective, but again, it depends upon the specific application. I did a synthesizer mixer with no tuned circuits to get from 40 MHz crystal oscillator to 220MHz to mix down a VCO to an IF for the programmable divider. Was really sweet! Did the same for what I believe was the very first synthesized 2M hand held in 1973. A Motorola HT220. Even had the Transmit VCO _ON_ yes _ON_ the TX frequency. Total current drain was 7ma. Tx spurious (-70dBc) better than the original (-35-40dB) Still have it. -- Steve N, K,9;d, c. i My email has no u's. "Jim Thompson" wrote in message ... On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote: I think it boils down to something very practical: ...It becomes a matter of how close and how large the undesired spectral components are compared to the desired spectral components. ... As an example, a x4 multiplier stage will have a desired output at Fin x 4, and close-in undesired products at Fin x 3 and Fin x 5. ... Joe, W3JDR [snip] I would think a "W3JDR" would know that even harmonics are *much* harder to obtain in nonlinear multipliers. ...Jim Thompson |
On Mon, 16 Feb 2004 10:19:49 -0700, Jim Thompson
wrote: It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. --- 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. -- John Fields |
On Mon, 16 Feb 2004 10:19:49 -0700, Jim Thompson
wrote: It depends on what your are starting from. If it's a sine wave, yes even harmonics can be made from diode non-linearities. The OP has a inverter-style XTAL oscillator, output very nearly square. A square wave is rich in odd harmonics, a perfect square wave has NO even harmonics. --- 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. -- John Fields |
See my previous post. What is your application? That would help get better
advise. -- Steve N, K,9;d, c. i My email has no u's. "Paul Burridge" wrote in message ... On Sun, 15 Feb 2004 16:46:32 -0700, Jim Thompson wrote: On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? I suppose it boils down to how much signal is left in the mush as the harmonics get higher and higher. Knew I shoulda held on to that spectrum analyser I used to have. :-( I suppose that's the proper answer though: get the rise/fall times as small and possible, measure the specral output and pick a suitable harmonic with enough energy in it to set it 'comfortably' above the noise floor? -- The BBC: Licensed at public expense to spread lies. |
See my previous post. What is your application? That would help get better
advise. -- Steve N, K,9;d, c. i My email has no u's. "Paul Burridge" wrote in message ... On Sun, 15 Feb 2004 16:46:32 -0700, Jim Thompson wrote: On Sun, 15 Feb 2004 23:48:47 +0000, 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.) You ought to be able to answer that yourself... what's the spectral roll-off of a square wave ?? I suppose it boils down to how much signal is left in the mush as the harmonics get higher and higher. Knew I shoulda held on to that spectrum analyser I used to have. :-( I suppose that's the proper answer though: get the rise/fall times as small and possible, measure the specral output and pick a suitable harmonic with enough energy in it to set it 'comfortably' above the noise floor? -- The BBC: Licensed at public expense to spread lies. |
" 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." Oh yuchh...that sounds painful! Why not just distort the symmetry of the square digitally (like drive it into an exclusive-or with a small delay on one input) to make a short impulse, then bandpass filter the output? Or staying in the purely digital domain, use same said exclusive-or and delay one of the two inputs by t/4 (t=period of input sq wave) and get a 2*F square wave out. Joe W3JDR |
" 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." Oh yuchh...that sounds painful! Why not just distort the symmetry of the square digitally (like drive it into an exclusive-or with a small delay on one input) to make a short impulse, then bandpass filter the output? Or staying in the purely digital domain, use same said exclusive-or and delay one of the two inputs by t/4 (t=period of input sq wave) and get a 2*F square wave out. Joe W3JDR |
In article , Paul Burridge
writes: 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.) Paul, past state of the hardware art (past 60 years) indicates that triplers are the practical maximum. Quintuplers have been done but those are rare in described applications. In 1955 I had hands-on experience with a septupler (7 x multiplier) using a 2C39 and a cavity-tuned plate circuit at 1.8 GHz. That was in a General Electric microwave radio relay terminal designed about 1950. Of nine terminals, two had to "QSY" to new crystal-controlled microwave center frequencies for second-level contingency operation. Difficult and fussy to do but was do-able...the crystal was also 7th overtone in a vacuum tube oscillator but was followed by a buffer stage feeding a tripler, another buffer, then the septupler which fed another 2C39 as the pulse-modulated final for 12 W peak output at 1.8 GHz. [from memory and 35mm slides...big GE manual went to recycle a long time ago] That's the only septupler application that I am aware of...no doubt there are others, somewhere. General Electric must have had some division/work-group with lots of work in old frequency control methods. A local NTSC color sub- carrier generator-regenerator made by GE had extensive use of "locked oscillators" for frequency multiplication and division, but mostly at frequencies lower than 7 MHz. Haven't come across any practical hardware on locked oscillators except for two mentions in older journals, trade papers. One of those used transistors as active devices. Doublers and quadruplers have been made using both diodes and tube-or-transistor active devices. That's relatively easy with non- square waveforms (distorted sinewaves); square waves have high odd harmonic energy, low even harmonic energy. 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. :-) Digital division IS straightforward up to about 1 GHz based on such technology over the last 3 decades. That's why PLLs came to prominence in frequency control techniques up to UHF. Len Anderson retired (from regular hours) electronic engineer person |
In article , Paul Burridge
writes: 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.) Paul, past state of the hardware art (past 60 years) indicates that triplers are the practical maximum. Quintuplers have been done but those are rare in described applications. In 1955 I had hands-on experience with a septupler (7 x multiplier) using a 2C39 and a cavity-tuned plate circuit at 1.8 GHz. That was in a General Electric microwave radio relay terminal designed about 1950. Of nine terminals, two had to "QSY" to new crystal-controlled microwave center frequencies for second-level contingency operation. Difficult and fussy to do but was do-able...the crystal was also 7th overtone in a vacuum tube oscillator but was followed by a buffer stage feeding a tripler, another buffer, then the septupler which fed another 2C39 as the pulse-modulated final for 12 W peak output at 1.8 GHz. [from memory and 35mm slides...big GE manual went to recycle a long time ago] That's the only septupler application that I am aware of...no doubt there are others, somewhere. General Electric must have had some division/work-group with lots of work in old frequency control methods. A local NTSC color sub- carrier generator-regenerator made by GE had extensive use of "locked oscillators" for frequency multiplication and division, but mostly at frequencies lower than 7 MHz. Haven't come across any practical hardware on locked oscillators except for two mentions in older journals, trade papers. One of those used transistors as active devices. Doublers and quadruplers have been made using both diodes and tube-or-transistor active devices. That's relatively easy with non- square waveforms (distorted sinewaves); square waves have high odd harmonic energy, low even harmonic energy. 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. :-) Digital division IS straightforward up to about 1 GHz based on such technology over the last 3 decades. That's why PLLs came to prominence in frequency control techniques up to UHF. Len Anderson retired (from regular hours) electronic engineer person |
On Mon, 16 Feb 2004 19:40:00 GMT, "W3JDR" wrote:
" 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." Oh yuchh...that sounds painful! --- Just making a point for Mr. T. :-) Why not just distort the symmetry of the square digitally (like drive it into an exclusive-or with a small delay on one input) to make a short impulse, then bandpass filter the output? Or staying in the purely digital domain, use same said exclusive-or and delay one of the two inputs by t/4 (t=period of input sq wave) and get a 2*F square wave out. --- Sure, why not? -- John Fields |
On Mon, 16 Feb 2004 19:40:00 GMT, "W3JDR" wrote:
" 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." Oh yuchh...that sounds painful! --- Just making a point for Mr. T. :-) Why not just distort the symmetry of the square digitally (like drive it into an exclusive-or with a small delay on one input) to make a short impulse, then bandpass filter the output? Or staying in the purely digital domain, use same said exclusive-or and delay one of the two inputs by t/4 (t=period of input sq wave) and get a 2*F square wave out. --- Sure, why not? -- John Fields |
In article , "W3JDR"
writes: This is a multi-part message in MIME format. ------=_NextPart_000_00CD_01C3F49A.C1DF8CA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable " 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." =20 Oh yuchh...that sounds painful!=20 Why not just distort the symmetry of the square digitally (like drive it = into an exclusive-or with a small delay on one input) to make a short = impulse, then bandpass filter the output? Or staying in the purely = digital domain, use same said exclusive-or and delay one of the two = inputs by t/4 (t=3Dperiod of input sq wave) and get a 2*F square wave = out. ...or just use a small toroid transformer, a pair of diodes arranged like a full-wave rectifier for wideband frequency doubling? :-) While using digitial techniques sounds cool at first, the above technique can generate all kinds of PM that isn't noticed on time- domain viewing with a scope. There are many ways to cure that PM or incidental FM but all involve lots more circuitry than the simple diode doubler which can be inherently broadband over half an octave. Depends on the application of the multiplier and the overall specs on purity of the multiplied RF. Len Anderson retired (from regular hours) electronic engineer person |
In article , "W3JDR"
writes: This is a multi-part message in MIME format. ------=_NextPart_000_00CD_01C3F49A.C1DF8CA0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable " 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." =20 Oh yuchh...that sounds painful!=20 Why not just distort the symmetry of the square digitally (like drive it = into an exclusive-or with a small delay on one input) to make a short = impulse, then bandpass filter the output? Or staying in the purely = digital domain, use same said exclusive-or and delay one of the two = inputs by t/4 (t=3Dperiod of input sq wave) and get a 2*F square wave = out. ...or just use a small toroid transformer, a pair of diodes arranged like a full-wave rectifier for wideband frequency doubling? :-) While using digitial techniques sounds cool at first, the above technique can generate all kinds of PM that isn't noticed on time- domain viewing with a scope. There are many ways to cure that PM or incidental FM but all involve lots more circuitry than the simple diode doubler which can be inherently broadband over half an octave. Depends on the application of the multiplier and the overall specs on purity of the multiplied RF. Len Anderson retired (from regular hours) electronic engineer person |
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. OTOH, if you have had some bad experiences with diodes in the past, I can easily understand your tendency to abuse them as often as you can. Jim |
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. OTOH, if you have had some bad experiences with diodes in the past, I can easily understand your tendency to abuse them as often as you can. Jim |
I read in sci.electronics.design that John Fields jfields@austininstrum
ents.com wrote (in ) about 'Frequency multiplication', on Mon, 16 Feb 2004: 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. No need to abuse any diodes. The third harmonic is already there, just 10 dB down. You only need a bit of gain after the peaky filter. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk |
I read in sci.electronics.design that John Fields jfields@austininstrum
ents.com wrote (in ) about 'Frequency multiplication', on Mon, 16 Feb 2004: 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. No need to abuse any diodes. The third harmonic is already there, just 10 dB down. You only need a bit of gain after the peaky filter. -- Regards, John Woodgate, OOO - Own Opinions Only. The good news is that nothing is compulsory. The bad news is that everything is prohibited. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk |
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 |
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