A Basic Study on a Resonance Characteristics of the Whispering Gallery Mode on a Layered Dielectric Disks Resonator

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A subject of our research is to apply a layered dielectric disks resonator operated by Whispering Gallery Modes to a band pass filter in millimeter wave band. Upper (lower) disk is separated from lower (upper) one by an air gap length d.In 2001, we concluded from experiments in microwave region that the above stated structure was applicable to the band pass filter. In 2002, we had been progressing in our research. Namely, we could estimate a coupling coefficient between coupled two dielectric disks and external Q value from a design theory for filter. It was found from our investigations that we could realize a desired band pass filter by giving a center frequency and band width. In electromagnetic theory, we used an approximated separation variables method, which had been proposed by the head investigator of this research, to calculate the coupling coefficient of coupled two dielectric disks. From these examination, we could decide the air gap length d and a distance s from the disk to a rectangular dielectric waveguide which was used to excite the disk. We had also performed experiments to confirm our analytical usefulness and adequacy in millimeter wave band. A part of this Grant-in-Aid for Scientific Research was spent on a millimeter wave source module which was used in these experiments.As the whispering gallery modes resonator has many resonance frequencies, spurious band pass widths exist near the desired band pass width in the above stated structure. Then, we proposed another type of structure to suppress the spurious band pass widths. In new structure, different disks from the upper (lower) disk were substituted for the air gap. We confirmed experimentally that the new structure suppresses the spurious band pass strength about 20dB. ( Refer the first article in next page)