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Resources for Designing Cavity Resonators

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Taking a look at the HP 8640B sig gen and its cavity resonator main oscillator got me interested in cavity design. Does anyone have any good textbooks or other resources about either the EM cavity theory or practical design? I was taking a look at Pozar's book, but there's fewer than 10 pages on the subject. I was hoping for a little more! I suppose some of my main questions include how best to couple a (coaxial, for example) signal into a resonator and ideal methods for tuning.
If anyone has experience with designing tunable oscillators with cavity resonators, I'd be highly interested to hear about it too.


Zverev's book, "Handbook of Filter Synthesis" has some discussion of Helical Cavity filters in Section 9. Never designed a Cavity filter but used YIG devices in tunable oscillators, these are very interesting devices that operate based upon EM field theory.


The mit radlab series has some practical information on that, and is free online, as I recall.
Obviously it isn't modern, but some things never change, and if anything it's more from the
peak times of cavity r&d than things made in subsequent decades.

You could see if microwave journal, microwaves101 web site have relevant articles.

BSTJ probably has some, too, and it's also free online last I knew.

To couple coax to cavity often involves one of two approaches to actually launch the signal.

1: know what mode in the guide you're trying to excite and therefore also what modes exist in the physical spatial design of the guide, so you'll know where the E and H field maxima can be located geometrically and what their polarization is.

2: An E field probe can be just a finger like essentially a monopole antenna aligned with producing the mode of the E field you're trying to excite. Basically ground the braid of the coax to the guide's wall and extend the innner conductor into the guide straight or bent in an "L" shape after it clears the guide wall by a small amount so the section in free space away from the wall is aligned with producing the E field

3: An H field probe is similar except it is a loop like a "J" where the top of the J is conceptually axial with the coaxial inner conductor and the end tip of the J is connected well electrically to the inner wall of the guide, and the braid is electrically connected to the guide as before.  So you're forming a small loop antenna where the inner conductor forms a small coil that is electrically returned to the guide wall more or less opposite where the braid is attached.  The inductance couples the H field aligned with the mode polarization you want to excite.

In either case you can adjust:
A: alter the length of the probe feed conductor inside the guide from "tiny" to "small".
B: rotate the physical angle of the loop / monopole a bit relative to the guide field mode.
C: Move the feed point closer to or away from the line of the guide where the H/E field maxima occurs.
D: Move the feed point closer to or away from the end of the guide where presumably your reflecting wall end cap is.

...so that the degree of coupling is adjusted and the coupling impedance can be changed.

Oh you might also check these, they may have something useful; I'll see about checking my paper copies in a while but in the mean time:

Measurements at centimeter wavelenghts

Microwave spectroscopy (has something about probes / launchers / couplers etc. as I recall)

Very high frequency techniques (?):

Terman's radio engineering handbook (probably not a lot of content but maybe something useful)

ARRL handbook (probably not a lot of content)



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