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#15
February 24th 04, 05:58 AM
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In article , "Jan-Martin Noeding,
LA8AK" writes: On 22 Feb 2004 20:39:33 GMT, (Avery Fineman) wrote: Sorry. If you are using the passive diode doubler looking like a full-wave rectifier circuit, and you have a symmetric square wave, the only harmonics you get are from the transition edges. Symmetric square waves have very low even harmonic energy content; harmonics are in the odd harmonic frequencies. A non-symmetric rectangular (not a 'square') waveform has more even-harmonic energy content. with some experience you might say something else. Even harmonics are 'harmonics' too OK...I'll reset my time machine and do another 52 years in the business... :-) :-) :-) and for many purposes it is an advantage when the odd harmonic content is low Outside of a step-recovery diode multiplier for an L-band sampler-locked oscillator worked on about 1974 (oscillator at about 1.6 GHz), I've not found much even harmonic content from a symmetric square wave. Unsymmetric digital signals haven't been found to have much more even harmonic content than odd harmonit content when viewed on a spectrum analyzer...until the digital signal pulse width is VERY short compared to its repetition time. The SRD is able to get about as short as such pulses go and the duty cycle is in fractions of a percent. [also "avalanche diode" which I'm sure that someone will bring up sooner or later to start another argument...:-) ] The original question was about "practical multiplier stages." Those would range from doublers to quintuplers. Going much higher HAS been done but it takes VERY expensive lab instruments to prove them out, such as with an SRD "comb generator." Comb generators have all sorts of harmonics but trying to extract, say, the 21st without passing the 20th or 22nd harmonic requires a very fussy high-Q filter. Some of the things _possible_ are not quite in the homebrewer workshop category...or they take a LOT of time to complete. I mentioned the passive diode doubler for the simple reason it IS simple when used with a distorted sinewave source (not a square wave). The effect of the two diodes in a "full-wave rectifier like" circuit creates an artificial 2nd harmonic by adding one sinusoid swing with the other, opposite-polarity sinusoid swing inverted by transformer action. Jim Pennell commented on that previously (and quite correctly). That makes for a broadband, non-fussy doubler circuit. Old thing and not a super whiz-bang state-of-the- art, hot-off-the-drawing-board wonder but it works. :-) Len Anderson retired (from regular hours) electronic engineer person |
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