Quasidielectric Resonator, Novel Component for Microwave Filters.

In the guide system of a circular waveguide with a dielectric central lead (rod, wire) the attenuation of the E//0//m-wave (TM//0//m mode, m equals 1, 2, 3, . . . ) decreases with increasing dielectric constant of the rod if the rod diameter as a function of the material constants ( mu //1, epsilon //1 for the rod, mu //2, epsilon //2 for the medium between rod and metal tube) and the specific operation frequency is always so chosen that a field distribution determined by power functions is estrablished between rod and tube wall (TEM-wave). If such a configuration is utilized as a resonator, the characteristic Q-factor may considerably surmount the Q-factor cot delta of the employed dielectric material ( delta equals loss angle). By means of this concept, miniaturized filter structures of very high selectivity and extremely low attenuation can be constructed. The quasidielectric resonator exactly corresponds to a conventional coaxial resonator whose central conductor exhibits an infinitely high conductivity and thus can be considered as superconductive.