High-Q sapphire-rutile frequency-temperature compensated microwavedielectric resonators

摘要

A sapphiro-rutile composite resonator was constructed from ancylindrical sapphire monocrystal with two thin disks of monocrystalnrutile held tightly against the ends. Because rutile exhibits low lossnand an opposite temperature coefficient of permittivity to sapphire, itnis an ideal material for compensating the frequency-temperaturendependence of a sapphire resonator. Most of the electromagnetic modes innthe composite structure exhibited turning points (or compensationnpoints) in the frequency-temperature characteristic. The temperatures ofncompensation for the WG quasi TM modes were measured to be below 90 Knwith Q-factors of the order of a few million depending on the mode. FornWG quasi TE modes, the temperatures of compensation were measured to benbetween 100 to 160 K with Q-factors of the order of a few hundreds ofnthousands, depending on the mode. The second derivatives of thencompensation points were measured to be of the order 0.1 ppm/K2n, which agreed well with the predicted values