Terminology Clarification Request

Thread Starter

thebruce

Joined Dec 10, 2016
14
Hello All,
While I commonly lurk here, I am primarily interested in RF heating. I enjoy reading published RF literature in an effort to acquire sufficient knowledge to begin building simple circuits as a hobby. I apologize in advance for posting overly simple questions but in my development quest I often stumble on terms (and technical slang) that require a lot of research to unravel and often lead me to incomplete understanding in that my limited breadth of knowledge often does not finally apprehend intended meaning. While I am generally hesitant to post remedial questions, after some reading I still think I may still be missing the point.

Nathan O. Sokal - “CLASS-E HIGH-EFFICIENCY RF/MICROWAVE POWER AMPLIFIERS: PRINCIPLES OF OPERATION, DESIGN PROCEDURES, AND EXPERIMENTAL VERIFICATION” - in the abstract the author refers to a low order Class B circuit and upublished higher order Class B circuits having “improved-accuracy explicit design equations…, optimization principles, experimental results, tuning procedures, and gate/base driver circuits.” … This paper includes an accurate new equation for P that includes the effect of QL .

May I somewhat safely assume the low/high order referred to primarily pertains to the power transmitted (roughly V * I) or am I missing another meaning all together?

Thanks in advance
HAB
 

nsaspook

Joined Aug 27, 2009
7,281
Not my area of expertise but a quick search finds this.
https://people.physics.anu.edu.au/~dxt103/160m/class_E_amplifier_design.pdf
Result: The waveforms never have high voltage and high current simultaneously. The voltage and current switching transitions are time-displaced from each other, to accommodate transistor switching transition times that can be substantial fractions of the RF period. Turn-on transitions may be up to about 30% of the period and turn-off transitions up to about 20% of the period. The low-order Class-E amplifier of Fig 2 generates voltage and current waveforms that approximate the conceptual “target” waveforms in Fig 1; Fig 3 shows the actual waveforms in that circuit. Note that those actual waveforms meet all six criteria listed above and illustrated in Fig 1. Unpublished higher-order versions of the circuit approximate more closely the target waveforms of Fig 1, making the circuit even more tolerant of component parasitic resistances and nonzero switching-transition times.
The order seems to be the circuit fidelity of the driving waveform to a optimized class-E waveform.
 

Thread Starter

thebruce

Joined Dec 10, 2016
14
SO...in layman's terms the low/high order differentiation is based on wave forms rather than the cumulative magnitude of power? To me this would imply that higher order more nearly replicates theoretical wave shapes/timing in support of his stated goal to prove (or improve comfort with) "a priori" design as something that should minimise "fiddling with" (which reads to an entrepreneur as potentially uncontrollable soft costs). I recall reading a periodical article (sorry no url/reference) about the leap of faith often required to bring RF designs to fruition that supports your explanation. Something akin to "good enough" in open source programming prior to the application of the "thousand eyes" phenomena/principle. Again, an impediment to investment.
Many thanks to you for your kind explanation. I take your gentle hint to post the article in the future.
 

DarthVolta

Joined Jan 27, 2015
446
I gotta start learning past 1st-2nd year physics (on the equation level that is. I've read the books by scienstists, since I was a kid). I have lot's of book on it, and there's ton's online. So in all of human history, there's no easier time than now.
 

Thread Starter

thebruce

Joined Dec 10, 2016
14
100 kHz is not really RF, just nervous DC
Funny...no really...funny.
When I speak of RF heating (the kind mentioned in the referenced article) it's dipole excitement (primarily of water in my use case) which is absolutely not induction related as I understand/define induction or attempt to calculate it. It's a completely different set of formulas and branch of physics (in my experience). The article referenced is about high efficiency push/pull class E amplifiers operating in the UHF (ultra high frequency - now a misnomer) RF bands (generally between 1 and 100mHz or so...it varies depending on the source you choose) My particular interest is in the fixed ISM band at 13.56 mHz and pushing ~10Kw as a heat source for industrial processes.
 

Thread Starter

thebruce

Joined Dec 10, 2016
14
Funny...no really...funny.
When I speak of RF heating (the kind mentioned in the referenced article) it's dipole excitement (primarily of water in my use case) which is absolutely not induction related as I understand/define induction or attempt to calculate it. It's a completely different set of formulas and branch of physics (in my experience). The article referenced is about high efficiency push/pull class E amplifiers operating in the UHF (ultra high frequency - now a misnomer) RF bands (generally between 1 and 100mHz or so...it varies depending on the source you choose) My particular interest is in the fixed ISM band at 13.56 mHz and pushing ~10Kw as a heat source for industrial processes.
I suspect what you are referring to would be the frequency of the gate drives which operate the switching of the MOSFETs or IGBTs.
 
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