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On Sat, 13 Mar 2004 11:50:13 +0000, Paul Burridge
wrote: On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Not quite, no. Why would that make any difference? As the duty cycle deviates from 50%, the even harmonics start to appear, so you need a better filter to keep them out. John |
In article ,
John Larkin wrote: [....] As the duty cycle deviates from 50%, the even harmonics start to appear, so you need a better filter to keep them out. Also as you get nearer the 20-80 duty cycle the amplitude of the 5th harmonic decreases. -- -- forging knowledge |
In article ,
John Larkin wrote: [....] As the duty cycle deviates from 50%, the even harmonics start to appear, so you need a better filter to keep them out. Also as you get nearer the 20-80 duty cycle the amplitude of the 5th harmonic decreases. -- -- forging knowledge |
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:
The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:
The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. -- The BBC: Licensed at public expense to spread lies. |
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John Larkin ) writes:
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. But if you want to filter the 5th, it's mighty handy not to have nuch 4th or 6th around. But one of the problems Paul seems to be having, on an ongoing basis, is the lack of a historical perspective. He's going the digital route because that's where he comes from, and therefore he extends the idea. But anyone of us who have been around for a while, or even has just spent time with older books and magazines, knows that RF multipliers was done all the time before digital circuits had made much inroad. WItness the thread about VXOs a while back. He started with a digital oscillator, again because that's all he knows, and then sets out to pull it as much as possible. But this too has been done before, and doing some research in older ham magazines would have shown the problems and solutions. Maybe "oldtimers" are biased towards what they grew up with. But I see time after time in the sci.electronics.* hierarchy people wanting to do RF and see it as simply extending audio or digital concepts they already know. So they suddenly need a 5MHz oscillator, and wonder why they aren't having success with a function generator type IC, where the needed frequency is at it's upper limit. "How can I make an active filter at 10MHz" is not usually someone who has a specific need for an active filter at that frequency, but from someone who is used to active filters and has yet to see their limitations, or maybe more importantly, are unaware of what's normally done at RF. A coil is pretty bulky at 1KHz, but at 10MHz it's downright easy to wind. And I do find it interesting, to see fairly complicated answers for problems that were solved a long time ago, simply by coming from a different angle. Michael VE2BVW |
John Larkin ) writes:
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. But if you want to filter the 5th, it's mighty handy not to have nuch 4th or 6th around. But one of the problems Paul seems to be having, on an ongoing basis, is the lack of a historical perspective. He's going the digital route because that's where he comes from, and therefore he extends the idea. But anyone of us who have been around for a while, or even has just spent time with older books and magazines, knows that RF multipliers was done all the time before digital circuits had made much inroad. WItness the thread about VXOs a while back. He started with a digital oscillator, again because that's all he knows, and then sets out to pull it as much as possible. But this too has been done before, and doing some research in older ham magazines would have shown the problems and solutions. Maybe "oldtimers" are biased towards what they grew up with. But I see time after time in the sci.electronics.* hierarchy people wanting to do RF and see it as simply extending audio or digital concepts they already know. So they suddenly need a 5MHz oscillator, and wonder why they aren't having success with a function generator type IC, where the needed frequency is at it's upper limit. "How can I make an active filter at 10MHz" is not usually someone who has a specific need for an active filter at that frequency, but from someone who is used to active filters and has yet to see their limitations, or maybe more importantly, are unaware of what's normally done at RF. A coil is pretty bulky at 1KHz, but at 10MHz it's downright easy to wind. And I do find it interesting, to see fairly complicated answers for problems that were solved a long time ago, simply by coming from a different angle. Michael VE2BVW |
budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. 'Tune for smoke' isn't an option for most new products, which have to be manufactured without hands. Better to pick a suitable duty cycle (or more likely a conduction time period in a digital circuit), that has an efficient 5th harmonic component, including delays, at low power levels. http://www.wenzel.com/pdffiles/choose.pdf RL |
budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. 'Tune for smoke' isn't an option for most new products, which have to be manufactured without hands. Better to pick a suitable duty cycle (or more likely a conduction time period in a digital circuit), that has an efficient 5th harmonic component, including delays, at low power levels. http://www.wenzel.com/pdffiles/choose.pdf RL |
Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output level you like. Whatever you do don't go for phase locked loops. Junk your Spice. It tells you nothing you didn't already ought to know. If you don't know it then you shouldn't be doing the job anyway. You must have plenty of room on the PCB. But why don't you invest in a 17.2 MHz quartz crystal. They're cheap enough. You've already spent more time and trouble on research and investigation. Cut your losses. Redundency is a serious crime. It degrades reliabilty. Reliability is Quality versus Time. Every individual component must serve a recognisable, readily understandable purpose. If it's not understood then it shouldn't be there. High Quality is adherence to the specified intended purpose. Now I suppose some bright spark will say deliberate redundency can improve reliability. But ONLY when all else has failed. ---- Reg. "Paul Burridge" wrote in message ... On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. -- The BBC: Licensed at public expense to spread lies. |
Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output level you like. Whatever you do don't go for phase locked loops. Junk your Spice. It tells you nothing you didn't already ought to know. If you don't know it then you shouldn't be doing the job anyway. You must have plenty of room on the PCB. But why don't you invest in a 17.2 MHz quartz crystal. They're cheap enough. You've already spent more time and trouble on research and investigation. Cut your losses. Redundency is a serious crime. It degrades reliabilty. Reliability is Quality versus Time. Every individual component must serve a recognisable, readily understandable purpose. If it's not understood then it shouldn't be there. High Quality is adherence to the specified intended purpose. Now I suppose some bright spark will say deliberate redundency can improve reliability. But ONLY when all else has failed. ---- Reg. "Paul Burridge" wrote in message ... On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. -- The BBC: Licensed at public expense to spread lies. |
On Fri, 12 Mar 2004 13:56:10 +0000, Paul Burridge
wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. All I can get apart from the fundamental is a strong third harmonic on 10.32Mhz, regardless of what I tune for. I've tried passing the osc output through two successive inverter gates to sharpen it up, but still nothing beyond the third appears after tuned amplification for the fifth. I no longer have a spectrum analyser so can't check for the presence of a decent comb of harmonics at the input to the multiplier stage but can only assume the fifth is well down in the mush for some reason. I could change the inverters for schmitt triggers and gain a couple of nS but can't see that making enough difference. What about sticking a varactor in there somewhere? Would its non-linearity assist or are they only any good for even order harmonics? Any suggestions, please. I'm stumped! :( Certain duty cycles contain better 5th harmonic component amplitudes. A graph of fourier components is a useful guide - http://www.wenzel.com/pdffiles/choose.pdf One precaution; the chart in this article does not include phase information - this can reverse - which may be important for timing. RL |
On Fri, 12 Mar 2004 13:56:10 +0000, Paul Burridge
wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. All I can get apart from the fundamental is a strong third harmonic on 10.32Mhz, regardless of what I tune for. I've tried passing the osc output through two successive inverter gates to sharpen it up, but still nothing beyond the third appears after tuned amplification for the fifth. I no longer have a spectrum analyser so can't check for the presence of a decent comb of harmonics at the input to the multiplier stage but can only assume the fifth is well down in the mush for some reason. I could change the inverters for schmitt triggers and gain a couple of nS but can't see that making enough difference. What about sticking a varactor in there somewhere? Would its non-linearity assist or are they only any good for even order harmonics? Any suggestions, please. I'm stumped! :( Certain duty cycles contain better 5th harmonic component amplitudes. A graph of fourier components is a useful guide - http://www.wenzel.com/pdffiles/choose.pdf One precaution; the chart in this article does not include phase information - this can reverse - which may be important for timing. RL |
On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. John |
On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. John |
On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote: On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif --- That's close enough to 50% that you should have no problem generating and extracting a fifth harmonic. --- This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif --- If you've got the cap and resistor in series with the base, and no other circuitry in there, then what you're doing is half-wave rectifying the square wave in the base-to-emitter diode, and that's what you're seeing, along with what looks like some AC at the fundamental riding on the falling peaks and rising valleys of the square wave. The reason you can't see the fifth harmonic is because it's far enough down that everything else is so much higher in voltage that it's essentially down in the mud. If you want the fifth out, you'll have to extract it using a filter of some sort, the easiest being a series tuned trap or a parallel tuned tank. Why don't you post your schematic so we can see exactly what you're doing? --- Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. --- That'll probably do it, but it needs to go on the output of the multiplier, not between the square wave generator and the input, I think. Again, why don't you post a schematic of what you're up to? Please?-) -- John Fields |
On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote: On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif --- That's close enough to 50% that you should have no problem generating and extracting a fifth harmonic. --- This other trace was snapped at the base of the transistor stage that does the multiplying. All there is (circuitry-wise) between this trace and the last one is a 330 ohm series resistor and a 47pF cap. I'd have expected to see some clamping action due to the b/e junction, but the waveshape seems very odd - but does concur with the Spice simulation. Is there anything amiss, here? (Setting here is 0.5V/div) http://www.burridge8333.fsbusiness.co.uk/trace2.gif --- If you've got the cap and resistor in series with the base, and no other circuitry in there, then what you're doing is half-wave rectifying the square wave in the base-to-emitter diode, and that's what you're seeing, along with what looks like some AC at the fundamental riding on the falling peaks and rising valleys of the square wave. The reason you can't see the fifth harmonic is because it's far enough down that everything else is so much higher in voltage that it's essentially down in the mud. If you want the fifth out, you'll have to extract it using a filter of some sort, the easiest being a series tuned trap or a parallel tuned tank. Why don't you post your schematic so we can see exactly what you're doing? --- Still not a sniff of a fifth! :-( Currently building Reg's 17.2Mhz BPF to see if that can expose it. --- That'll probably do it, but it needs to go on the output of the multiplier, not between the square wave generator and the input, I think. Again, why don't you post a schematic of what you're up to? Please?-) -- John Fields |
In article , Paul Burridge
writes: On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa) wrote: Fifth harmonic frequency multipliers do exist, but it's usually much easier to double and triple your way to the final frequency if possible. (You just discovered this, I think!) Yeah, but trying to get the 5th is hardly asking for the moon... In a way, it IS. Fifth harmonic of an infinitely sharp transition rectangular waveform is still low in energy compared to the fundamental. Chances are that a single stage using an active device as a quintupler will NOT be successful, transistor or tube (valve). Let's get to some specifics on this problem - 1. Let us know what you are using to determine whether or not a 5th harmonic exists. The lack of indication may be due to whatever it is (not a spectrum analyzer) being used. 2. Describe the multiplier stage in more detail and include an approximate level and impedance/admittance of the RF source. That would include supply rails and biasing. 3. Describe whatever is being used to select the 5th harmonic and inhibit the fundamental and other harmonics. There's lots of energy at many different frequencies floating around there and you only want one frequency. 4. Review again with us the output drive level requirements so we can get a handle on that. 5. If you are using an oscilloscope to measure the fundamental waveform, estimate the actual risetime/falltime based on the rise/fall times limits of the oscilloscope. That yields some basic data that can be applied to a Fourier series to determine the level of 5th harmonic energy you have to work with. [that will also reveal the approximate frequency limits of the scope] The lack of even harmonics is typical of push-pull stages ... if you are messing around with CMOS gates, you might try using a TTL gate (which pulls low much stronger than it pulls high) or an open collector TTL gate, both with smmallish (100-200 ohm) pull-up resistors for doubling. I've a reasonably fast Schmitt I'm going to stick in there in place of the 74HC04 before I resort to anything fancy (same pin-out). Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz? Because I don't have a rock lying about for that fundamental! Hint: A mixed 2x and 3x = 5x out if filtered to pass that. No lying- around rock needed. [not an optimum solution] Note: As already pointed out, a single PLL IC can do the job in the same PCB footprint. When frustration hits a peak, it's time to sit back away from the problem and do an objective review of what is the overall task and what you've accomplished so far and what you know about certain circuits fundamentals. General problem descriptions only result in general solutions without quantitative values needed for a specific application. I've found that NON-linear circuits (a multiplier stage is definietly in the non-linear category) take rather more development time than a linear circuit. There's lots of different things going on in a multiplier circuit and those have to be considered for the whole. Hopefully some supreme being here will spot a problem with the traces I've now posted... Try as we might in the depths of our frustrations, supreme beings tend not to intervene in us humans' petty affairs. :-) Len Anderson retired (from regular hours) electronic engineer person |
In article , Paul Burridge
writes: On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa) wrote: Fifth harmonic frequency multipliers do exist, but it's usually much easier to double and triple your way to the final frequency if possible. (You just discovered this, I think!) Yeah, but trying to get the 5th is hardly asking for the moon... In a way, it IS. Fifth harmonic of an infinitely sharp transition rectangular waveform is still low in energy compared to the fundamental. Chances are that a single stage using an active device as a quintupler will NOT be successful, transistor or tube (valve). Let's get to some specifics on this problem - 1. Let us know what you are using to determine whether or not a 5th harmonic exists. The lack of indication may be due to whatever it is (not a spectrum analyzer) being used. 2. Describe the multiplier stage in more detail and include an approximate level and impedance/admittance of the RF source. That would include supply rails and biasing. 3. Describe whatever is being used to select the 5th harmonic and inhibit the fundamental and other harmonics. There's lots of energy at many different frequencies floating around there and you only want one frequency. 4. Review again with us the output drive level requirements so we can get a handle on that. 5. If you are using an oscilloscope to measure the fundamental waveform, estimate the actual risetime/falltime based on the rise/fall times limits of the oscilloscope. That yields some basic data that can be applied to a Fourier series to determine the level of 5th harmonic energy you have to work with. [that will also reveal the approximate frequency limits of the scope] The lack of even harmonics is typical of push-pull stages ... if you are messing around with CMOS gates, you might try using a TTL gate (which pulls low much stronger than it pulls high) or an open collector TTL gate, both with smmallish (100-200 ohm) pull-up resistors for doubling. I've a reasonably fast Schmitt I'm going to stick in there in place of the 74HC04 before I resort to anything fancy (same pin-out). Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz? Because I don't have a rock lying about for that fundamental! Hint: A mixed 2x and 3x = 5x out if filtered to pass that. No lying- around rock needed. [not an optimum solution] Note: As already pointed out, a single PLL IC can do the job in the same PCB footprint. When frustration hits a peak, it's time to sit back away from the problem and do an objective review of what is the overall task and what you've accomplished so far and what you know about certain circuits fundamentals. General problem descriptions only result in general solutions without quantitative values needed for a specific application. I've found that NON-linear circuits (a multiplier stage is definietly in the non-linear category) take rather more development time than a linear circuit. There's lots of different things going on in a multiplier circuit and those have to be considered for the whole. Hopefully some supreme being here will spot a problem with the traces I've now posted... Try as we might in the depths of our frustrations, supreme beings tend not to intervene in us humans' petty affairs. :-) Len Anderson retired (from regular hours) electronic engineer person |
In article , budgie
writes: On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. All I can get apart from the fundamental is a strong third harmonic on 10.32Mhz, regardless of what I tune for. In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. Fifty years ago that was mostly true and multiplier stages rarely went beyond the 4th harmonic. Two notable exceptions, though - A circa 1950 design by General Electric for an 1800 MHz radio relay terminal used a SEPTUPLER via a 2C39 planar triode. [7 x multiplier] Roughly 260 MHz input following a buffer stage from a 5th overtone crystal oscillator. Used in both transmitter and receiver panels ("dish- pan" style, chassis = rack panel) with the receiver septupler driving the mixer. Fussy to tune but stayed there once tuned. Another G.E. design of the early 1950s used Locked Oscillators in a TV broadcast local color subcarrier supply. Locked oscillators operate on integral multiples of the input and their use was almost extinct back then. That was deemed necessary in the G.E. design for an 11 x multiplier, the highest direct multiple I've encountered. A locked oscillator can also operate as a divider as G.E. did. The 3.58 MHz crystal could also be phase-locked to a network feed color burst. However, all those multiplier types went the way of the dinosaur when PLLs operating directly at the desired frequency came into being. There isn't any advantage to using those old "exotic" technologies other than in restoration for nostalgia's sake. Quintuplers CAN be made, but, so far, Paul hasn't explained enough specifics about his circuit, or how he is sensing any 5th harmonic for any of us to get a good handle on a possible aid. Note: Lacking any spectrum analyzer, a wide-range HF receiver with an S meter can be an indicator...but such needs to be checked against a calibrated signal generator for compensation of varying S meter indication versus input levels. That's what I use for checking HF levels (Icom R70) and it has been calibrated against a reasonably-known-level RF source. Len Anderson retired (from regular hours) electronic engineer person |
In article , budgie
writes: On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote: Paul Burridge wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far failing spectacularly. I've tried everything I can think of so far to no avail. All I can get apart from the fundamental is a strong third harmonic on 10.32Mhz, regardless of what I tune for. In RF circles, the 'normal' way to do this would be a simple Class C amplifier with a collector load tuned to the fifth harmonic. In calls C, conduction only occurs for a small fraction of a cycle which produces a correspondingly higher proportion of higher harmonics than a square wave. I've been waiting for someone to post this. I would only add "The drive level, and the bais point, will vary the amount of fifth (or whichever) you will see." It's as common as noses in RF, as Ian pointed out. Just look at the average two-way radio prior to frequency synthesisers. Crystal freqs were multiplied this way in transmitter chains and for receive injection, although use of fifth wasn't especially common because you normally had enough design control to use the more efficient *2, *3 or *4. Fifty years ago that was mostly true and multiplier stages rarely went beyond the 4th harmonic. Two notable exceptions, though - A circa 1950 design by General Electric for an 1800 MHz radio relay terminal used a SEPTUPLER via a 2C39 planar triode. [7 x multiplier] Roughly 260 MHz input following a buffer stage from a 5th overtone crystal oscillator. Used in both transmitter and receiver panels ("dish- pan" style, chassis = rack panel) with the receiver septupler driving the mixer. Fussy to tune but stayed there once tuned. Another G.E. design of the early 1950s used Locked Oscillators in a TV broadcast local color subcarrier supply. Locked oscillators operate on integral multiples of the input and their use was almost extinct back then. That was deemed necessary in the G.E. design for an 11 x multiplier, the highest direct multiple I've encountered. A locked oscillator can also operate as a divider as G.E. did. The 3.58 MHz crystal could also be phase-locked to a network feed color burst. However, all those multiplier types went the way of the dinosaur when PLLs operating directly at the desired frequency came into being. There isn't any advantage to using those old "exotic" technologies other than in restoration for nostalgia's sake. Quintuplers CAN be made, but, so far, Paul hasn't explained enough specifics about his circuit, or how he is sensing any 5th harmonic for any of us to get a good handle on a possible aid. Note: Lacking any spectrum analyzer, a wide-range HF receiver with an S meter can be an indicator...but such needs to be checked against a calibrated signal generator for compensation of varying S meter indication versus input levels. That's what I use for checking HF levels (Icom R70) and it has been calibrated against a reasonably-known-level RF source. Len Anderson retired (from regular hours) electronic engineer person |
In addition to what John L. posted about adding in 4th and 6th
harmonics and making it harder to filter, if you have a 40% or 60% (or 20% or 80%) duty cycle, there will be NO fifth harmonic. From what you've posted, that likely is the crux of your problem. Cheers, Tom Paul Burridge wrote in message . .. On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Not quite, no. Why would that make any difference? I'd have thought any decent 'squarish wave' of the correct frequency with sharp rise/fall edges ought to do the trick? It's spewing out the 3rd quite nicely after all. How about I post a pic of the sig trace into the multiplier? I'll see if I can do that a bit later 2day... |
In addition to what John L. posted about adding in 4th and 6th
harmonics and making it harder to filter, if you have a 40% or 60% (or 20% or 80%) duty cycle, there will be NO fifth harmonic. From what you've posted, that likely is the crux of your problem. Cheers, Tom Paul Burridge wrote in message . .. On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote: The 5th harmonic should be only 14dB below the fundamental, although it will drop fairly quickly as the sides of the input square wave deviate from vertical. Does the 3.44MHz have a 50% duty cycle? Not quite, no. Why would that make any difference? I'd have thought any decent 'squarish wave' of the correct frequency with sharp rise/fall edges ought to do the trick? It's spewing out the 3rd quite nicely after all. How about I post a pic of the sig trace into the multiplier? I'll see if I can do that a bit later 2day... |
On Sat, 13 Mar 2004 17:45:23 +0000 (UTC), "Reg Edwards"
wrote: Here's the solution. Build a 17.2 one-transistor LC oscillator. It will easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output level you like. Whatever you do don't go for phase locked loops. Junk your Spice. It tells you nothing you didn't already ought to know. If you don't know it then you shouldn't be doing the job anyway. You must have plenty of room on the PCB. But why don't you invest in a 17.2 MHz quartz crystal. They're cheap enough. You've already spent more time and trouble on research and investigation. Cut your losses. Hi Reg, I'm not into cutting my losses and taking the easy way out; I wouldn't *learn* anything by doing so. This circuit *ought* to work and I hope to find out why it doesn't and remedy the situation. I can't build a 17.2Mhz osc. I need to start much lower to multiply up the 'pullability' of the fundamental to the best part of half a Meg. Try doing that with a quartz xtal at 17Mhz! Sorry, I mean no offence I know you're unaware of the background to this project. BTW, I've built the filter your s/ware designed and it works pretty much as advertised - bang on 17.2Mhz pass[1] and the third harmonic of the fundamental at just over 10Mhz is *well* down by a factor of 80X (sorry, can't be arsed to work out the dB equivalent). The coils I used to build it were designed with one of your other programs, BTW! Many thanks indeed. I urge anyone else reading this in r.r.a.hb to grab Reg's programs whilst they can; they're *extremely* useful and Reg deserves a vote of thanks from us all for taking the time and trouble to write them. [1] Significant spurious pass response at 13.2Mhz for some reason (probably my use of inappropriate capacitors for the sake of expediency - Spice didn't predict it) fortunately it just misses the fourth harmonic! -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 17:45:23 +0000 (UTC), "Reg Edwards"
wrote: Here's the solution. Build a 17.2 one-transistor LC oscillator. It will easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output level you like. Whatever you do don't go for phase locked loops. Junk your Spice. It tells you nothing you didn't already ought to know. If you don't know it then you shouldn't be doing the job anyway. You must have plenty of room on the PCB. But why don't you invest in a 17.2 MHz quartz crystal. They're cheap enough. You've already spent more time and trouble on research and investigation. Cut your losses. Hi Reg, I'm not into cutting my losses and taking the easy way out; I wouldn't *learn* anything by doing so. This circuit *ought* to work and I hope to find out why it doesn't and remedy the situation. I can't build a 17.2Mhz osc. I need to start much lower to multiply up the 'pullability' of the fundamental to the best part of half a Meg. Try doing that with a quartz xtal at 17Mhz! Sorry, I mean no offence I know you're unaware of the background to this project. BTW, I've built the filter your s/ware designed and it works pretty much as advertised - bang on 17.2Mhz pass[1] and the third harmonic of the fundamental at just over 10Mhz is *well* down by a factor of 80X (sorry, can't be arsed to work out the dB equivalent). The coils I used to build it were designed with one of your other programs, BTW! Many thanks indeed. I urge anyone else reading this in r.r.a.hb to grab Reg's programs whilst they can; they're *extremely* useful and Reg deserves a vote of thanks from us all for taking the time and trouble to write them. [1] Significant spurious pass response at 13.2Mhz for some reason (probably my use of inappropriate capacitors for the sake of expediency - Spice didn't predict it) fortunately it just misses the fourth harmonic! -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin
wrote: On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. You must have bloody good eyesight, John! :-) BTW, can you recommend a sub nS Schmitt inverter that's easily obtainable? -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin
wrote: On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. You must have bloody good eyesight, John! :-) BTW, can you recommend a sub nS Schmitt inverter that's easily obtainable? -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 12:50:42 -0600, John Fields
wrote: That's close enough to 50% that you should have no problem generating and extracting a fifth harmonic. Thanks, John. I'd have been surprised if having tweaked it for maximum 50:50 this still wasn't good enough (it's only a tiny bit out now). If you've got the cap and resistor in series with the base, and no other circuitry in there, then what you're doing is half-wave rectifying the square wave in the base-to-emitter diode, and that's what you're seeing, along with what looks like some AC at the fundamental riding on the falling peaks and rising valleys of the square wave. The reason you can't see the fifth harmonic is because it's far enough down that everything else is so much higher in voltage that it's essentially down in the mud. If you want the fifth out, you'll have to extract it using a filter of some sort, the easiest being a series tuned trap or a parallel tuned tank. I've lashed up a 17.2Mhz BPF that should do the trick just fine. It'll be a bit of a fiddle trying to hook it into the existing circuit but I'll do my best. Why don't you post your schematic so we can see exactly what you're doing? Will do.... -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 12:50:42 -0600, John Fields
wrote: That's close enough to 50% that you should have no problem generating and extracting a fifth harmonic. Thanks, John. I'd have been surprised if having tweaked it for maximum 50:50 this still wasn't good enough (it's only a tiny bit out now). If you've got the cap and resistor in series with the base, and no other circuitry in there, then what you're doing is half-wave rectifying the square wave in the base-to-emitter diode, and that's what you're seeing, along with what looks like some AC at the fundamental riding on the falling peaks and rising valleys of the square wave. The reason you can't see the fifth harmonic is because it's far enough down that everything else is so much higher in voltage that it's essentially down in the mud. If you want the fifth out, you'll have to extract it using a filter of some sort, the easiest being a series tuned trap or a parallel tuned tank. I've lashed up a 17.2Mhz BPF that should do the trick just fine. It'll be a bit of a fiddle trying to hook it into the existing circuit but I'll do my best. Why don't you post your schematic so we can see exactly what you're doing? Will do.... -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 12:50:42 -0600, John Fields
wrote: Again, why don't you post a schematic of what you're up to? Please?-) The schematic is now on abse.... -- The BBC: Licensed at public expense to spread lies. |
On Sat, 13 Mar 2004 12:50:42 -0600, John Fields
wrote: Again, why don't you post a schematic of what you're up to? Please?-) The schematic is now on abse.... -- The BBC: Licensed at public expense to spread lies. |
I read in sci.electronics.design that Reg Edwards
wrote (in et.com) about 'Extracting the 5th Harmonic', on Sat, 13 Mar 2004: Then along came Oliver Heaviside who turned the World upside down by replacing jw with p. I should probably change my name to Phon .oodgate in his honour. (;-) -- 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 Reg Edwards
wrote (in et.com) about 'Extracting the 5th Harmonic', on Sat, 13 Mar 2004: Then along came Oliver Heaviside who turned the World upside down by replacing jw with p. I should probably change my name to Phon .oodgate in his honour. (;-) -- 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 Sat, 13 Mar 2004 19:38:47 +0000, Paul Burridge
wrote: On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin wrote: On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. You must have bloody good eyesight, John! :-) You can count the graticule lines fairly well; it's close to 50%, and the edges are fairly fast. And no, in fact I have terrible eyesight. BTW, can you recommend a sub nS Schmitt inverter that's easily obtainable? I don't know of any really fast Schmitts. An HC14 followed by an AC04 should have fast edges. My favorite thing like this is an OnSemi NL37WZ16 with all three sections in parallel. Powered from +6 or so, it puts 5 volts into 50 ohms in something like 750 ps. The old original RCA AC-series parts were sub-ns - crude and rude, they were - but some ACs are now a little slower to reduce ground bounce. Most of the LVDS-to-TTL LVDS line receivers make damned fine comparators with sub-ns output edges. For screaming edges, there's always the step-recovery diode, or a medium-power gaasfet like the CLY2. John |
On Sat, 13 Mar 2004 19:38:47 +0000, Paul Burridge
wrote: On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin wrote: On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge wrote: Okay, I've now tweaked the osc. to get as near to 50% as possible. Alas, still no sign of any 5th present in the multiplier's output. Here's a shot of the (fundamental) output from the inverters. I can't see any real problem with why it shouldn't be good for a reasonable comb of harmonics, but our experts may know better. BTW, settings were 2V/div. and 0.1uS/div. http://www.burridge8333.fsbusiness.co.uk/trace.gif That waveform *has* bunches of 5th harmonic. All you need is a properly functioning bandpass filter to pluck it out. You must have bloody good eyesight, John! :-) You can count the graticule lines fairly well; it's close to 50%, and the edges are fairly fast. And no, in fact I have terrible eyesight. BTW, can you recommend a sub nS Schmitt inverter that's easily obtainable? I don't know of any really fast Schmitts. An HC14 followed by an AC04 should have fast edges. My favorite thing like this is an OnSemi NL37WZ16 with all three sections in parallel. Powered from +6 or so, it puts 5 volts into 50 ohms in something like 750 ps. The old original RCA AC-series parts were sub-ns - crude and rude, they were - but some ACs are now a little slower to reduce ground bounce. Most of the LVDS-to-TTL LVDS line receivers make damned fine comparators with sub-ns output edges. For screaming edges, there's always the step-recovery diode, or a medium-power gaasfet like the CLY2. John |
"Mike Andrews" wrote in message ... In (rec.radio.amateur.homebrew), Paul Burridge wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? The crystal osc itself, probably is sine wave, and therefore has low 5th content. Square it up, then pass through a filter, and moderate Q parallel resonant tank on the 5th harmonic. |
"Mike Andrews" wrote in message ... In (rec.radio.amateur.homebrew), Paul Burridge wrote: Hi all, Is there some black magic required to get higher order harmonics out of an oscillator? The crystal osc itself, probably is sine wave, and therefore has low 5th content. Square it up, then pass through a filter, and moderate Q parallel resonant tank on the 5th harmonic. |
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