GB752467A - Improvements in high dielectric constant ceramic cavity resonators - Google Patents

Abstract

752,467. Cavity resonators. ERIE RESISTOR CORPORATION. Feb. 25, 1954 [March 20, 1953; Nov. 13, 1953], No. 5559/54. Class 40 (8). A cavity resonator comprises a body of high dielectric-constant (about 1000 or more) ceramic material, e.g. barium titanate having an exciting loop or electrode metallized upon its surface. The disc-shaped titanate body 1 of Fig. 1 has holes 5, 6 whose metallized coatings are joined by a short metallized strip on the underside of the body 1. These coatings form an inductive loop whose magnetic field is directed circumferentially around the body 1 and between metallic coatings 2 on either side of the disc. The exciting loop in the resonator 1 of Fig. 3 consists of an arcuate strip of silver 21. The resonator 1 in this embodiment is uncoated, the discontinuity occurring at the boundary of the body due to its high dielectric constant being relied upon to confine the electromagnetic flux within the body. The loop 28 of the resonator of Fig. 5 extends across two sides of the dielectric body and is insulated from the metallized portions 24, 25 by unmetallized strips 26, 27. The metallic coatings 24, 25 extend over both sides of the body. A disc-shaped resonator may be excited electrostatically by means of an electrode situated on the centre of one face (Fig. 8, not shown). Alternatively the electrode may be formed by coating a central cylindrical recess 34, Fig. 9, in one face of the body. An insulated metallic boundary coating 38 may be applied to the body. The resonator of Fig. 11 is in the form of an annulus 40 excited by inductive loops 45, 46. A central cylindrical section 39 is made of a material whose Curie point is below normal operating temperature, e.g. a mixture of barium and strontium titanates. Application of a control voltage to electrodes 41, 42 enables the frequency of the resonator to be varied. The cylindrical resonator of Fig. 12 may be excited by an inductive loop 50 or by an electrode (not shown) coated on to the bottom of an arcuate slot in the curved side of the cylinder.