From: Paul
Date: Fri, 22 Dec 2000 08:54:16 +0000
Subject: Re: [TSSP] Coils at high elevation
boris petkovic wrote: > > > As fn resonant frequency increases situations change > > > -the effect of Cint influence to higher harmonic > > > frequency cannot be neglected anymore. > > > This year I sent Malcolm an outline of my papers > > > where I explained how and why that appears. > > Me: > > I'd like to see those. Boris: > In these papers ,among other things was shown that > influence of Cintrisic could be so dramatic that > something like very high, say 13th or 15th, resonant > frequency for usual no hat helical resonators actually > didn't exist. > In other words,capacitive network of winding acts on > incoming waves so dramaticaly that degenerates > formation of standing waves' notches and nodes. > After critical high frequency passed,voltage profile > over winding could be just a sort of hyperbolic > function and nothing more ,appearing and dissapering > in phase with driving source voltage function. Interesting. I've seen the higher resonances peter out to nothing and assumed it was just an effect of declining Q at higher frequencies. I've not trusted the simulator beyond about the 10th overtone due to it's limited spatial resolution of the physical Cext and Cint. Last night I explored up to 65th overtone using tsim, and the equal spacing between overtones apparent between say 4th and 15th overtones alters above about the 15th, the intervals gradually becoming larger and larger. This is on a very high Q coil. I assume this is an artifact of the simulator, but it sounds like I need to add exploration of this by measurement to the list of things to do! Boris, thanks for raising the point. What you are saying about Cint is making some sense to me. Perhaps we can think of Cint as bypassing and short-circuiting the inductance at higher frequencies. Clearly there is knowledge waiting to be gleaned from exploration of the higher overtones. I'll bet there is a formula to be found for a cut-off frequency. Wish I new how to work out a phase constant, either an average value for the coil, or as a function of position. Cheers, -- Paul Nicholson, Manchester, UK. --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.