GB1376938A - Composite dielectric resonator - Google Patents

Abstract

1376938 Dielectric resonators NIPPON HOSO KYOKAI 22 Nov 1971 [26 Nov 1970] 54069/71 Heading H1W A dielectric resonator comprises two bodies having temperature coefficients of relative dielectric constant of opposite sign and an interface parallel with the electric vector of the e-m field, whereby changes of resonant frequency with temperature are compensated. As shown (Fig. 15), the resonator consists of discs or rectangular blocks 81, 83 respectively of TiO 2 and LiNbO 3 supported on an element 85 of low dielectric constant between the ground conductors 73, 75 of a triplate strip-line 71, 73, 75. The resonator may support either the EH 11 or HE 11 wave modes, both of which have electric fields parallel to the interface between the bodies 81, 83. It is also possible to use a resonator in the form of a disc or elongated cylinder comprising inner and outer concentric bodies having the required properties, but such resonators cannot effectively utilize the HE 11 mode since the electric field of this mode does not lie parallel to the cylindrical interface between the two bodies. The bodies 81, 83 may comprise single crystals -preferably arranged such that their optical axes lie parallel to the interface. Since they have dielectric anisotropy, the dielectric constant measured in a direction parallel to the optical axis differs from that measured normal to this axis. Hence the resbnator may be turned by adjusting the angle between the optical axes of the bodies. For the same purpose, a thin, rotatable disc made of the material of one of the bodies may be mounted on the resonator. Tuning may also be accomplished by means of metallic screws 91, 93 which extend into the fringe field of the resonator. These affect the distribution of stored energy between the electric and magnetic fields within the bodies to which they are respectively adjacent. Hence the contribution of each of the bodies to the temperature-compensating effect may be varied and since these are of opposite sign, a zero temperature coefficient may be obtained for the whole resonator. In the modification of Fig. 20, the interface between bodies 101, 103 forming the resonator lies parallel to the short sides of a rectangular waveguide 100. The resonator is supported on a ceramic element 111 of low dielectric constant and is tuned by conductive plugs 113, 115. Both the constructions shown provide bandstop filters. In order to form a strip-line bandpass filter, the resonator is placed in the coupling region between adjacent, parallel ends of two short-circuited strip-lines (Figs. 21, 22, not shown). In order to provide a waveguide band-pass filter, the resonator is placed in a length of cut-off waveguide to which input and output circuits are coupled.