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I am no expert but I will recommend the requester to read some new textbook on resonators.
He will see that a cavity resonator with a high quality needs a large volume; the volume to cubed wavelength determines the spectrum line width. In resonator applications like in oscillators the narrow line width is preferred.
Dielectric resonators have developed in last 20-30 years mainly by introducing low-loss ceramic materials. This allowed to create very small resonators relative to a wavelength where they resonate. Filters and resonators at microwaves longer than an inch now need a very small space and dimensions.
Using ceramic dielectric resonators also allowed to compose the ceramic material (or combining two different parts of resonator body) so that resonance frequency does not vary with temperature.
Ceramic materials are now also used in antennas, delay lines, etc. All their advantages were a spinoff of dielectric resonator development.
They are much smaller than a mechanical cavity resonator, they do not depend on the external housing dimensions for frequency (so cover can deflect, etc), they are high Q.
Downside--they are not very tunable. You need to buy quality ones, because microcracks can ruin your whole day.
Mini-Circuits and UMC(now maybe MACOM or RFID, I can't assure it) have very good VCO using dielectric resonators, and have good performance to anti-microphone.
Hi,
Me too I'm trying to learn more about dielectric resonator.
In the enclosed pic You can see: a Gaasfet, some stripline, a dielectric resonator. The frequency out is 5.786 Ghz
The box is normally closed and a little screw just up the D.R. allow a small frequency shift (20/30 Mhz)
Very nice "toys" the Dielectric Resonators.
The really big problem is that if you need a particular frequency , You have to be (very) luck to find the right pill...
You are right: dielectric "pills" are manufactured for the particular frequency you need. More than that; for use in oscillators, their material composition is carefully adjusted to compensate temperature effects. In earlier versions, such temperature compensation was achieved by gluing together two pills with the temperature drifts going against each other, or the metal tuner was made of a metal with a dilatation set to compensate.
Like with quartz crystals (and a bit easier), you can grind the puck to move the resonant frequency. But for mass production, the pucks are rather selected from a quantity, to keep the cost low.
"Like with quartz crystals (and a bit easier), you can grind the puck to move the resonant frequency...."
Yeah, this has been one of my first try. First grind, then try the frequency by loosely coupling the pill to a small coil out of the tracking generator of the spectrum analyzer and read the difficult to see dip. But when you place and glue the "pill" in the box you get a different frequency.
Second try : I've placed and glued the "pill" on the box, screwed (twelve), tested the frequency, unscrewd ,grind, screw, test frequency and so on ... Sometime, may be the damned pill don't like me and became dead...
This is the reason about the luck I was talkin before.
With the quartz it was much more easy : grind with toothpaste for an higher frequency, paint carefully with graphite to lower the frequency
"Like with quartz crystals (and a bit easier), you can grind the puck to move the resonant frequency...."
Yeah, this has been one of my first try. First grind, then try the frequency by loosely coupling the pill to a small coil out of the tracking generator of the spectrum analyzer and read the difficult to see dip. But when you place and glue the "pill" in the box you get a different frequency.
Second try : I've placed and glued the "pill" on the box, screwed (twelve), tested the frequency, unscrewd ,grind, screw, test frequency and so on ... Sometime, may be the damned pill don't like me and became dead...
This is the reason about the luck I was talkin before.
With the quartz it was much more easy : grind with toothpaste for an higher frequency, paint carefully with graphite to lower the frequency
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