As cellular mobile communication systems' markets are expanding worldwide, miniaturization for the terminals are strongly required and accordingly the RF front end circuit components in the terminals are required to be much smaller. This markets' demand of miniaturization has provided a perfect opportunity for pushing forward with creating the components using dielectric ceramics. The miniaturization is realized by a sophisticated integration of techniques consisted of monoblock forming, multi-layer, electrode patterning and processing, MIC, electro-magnetic wave analysis oriented simulation, production and measurement based on dielectric ceramic materials. In this paper, examples of several filters and VCO developed using these techniques are picked up, the constructions and features are described, and technical prospects are discussed. They include monoblock type filters with additional coupling capacitors on the dielectric substrate, coaxial resonator type filters of rectangular coaxial dielectric resonator and its circuit theory, balanced double layer stripline type filter of substantial triplate structure using dielectrics of higher and lower permittivities, multilayer lumped constant filter and VCO by multi-layer, electrode patterning and simple circuit theory. The technologies are applicable to over-all 900MHz band mobile communication systems in the world, and these components are possibly miniaturized to less than 1 cm3, to be small enough for smaller-than-the-present-size portable telephones application.

A surface mount device (S. M. D.) type miniature isolator has been developed. Its dimension is 6.8 6.9 4 mm3 and weight is 0.75 g. Both the volume and weight have been reduced to one-third compared with a conventional small model. A resin case and metalplated terminals on its surface are used to realize this configuration. By using a simplified simulation technique the most suitable ferrite size and the most suitable magnet are determined to minimize an insertion loss and to realize good temperature stability. Consequently, 0.8 dB insertion loss, 15 dB isolation and 14 dB return loss are obtained within 3 % bandwidth at 836.5 MHz in the practical operating temperature range between -25 and +75. Handling power capability of 2.5 W for forward input and 0.75 W for reverse input are achieved at +25.

A miniaturized antenna duplexer for 800 MHz band cellular portable telephone terminal was developed by using copper-plated rectangular coaxial dielectric resonators. The duplexer with mechanically stable construction is realized and available to surface mount devices. The volume is 3.7 cc about one half of the volume of a conventional dielectric duplexer for E-TACS.

A novel hybrid numerical method, which is based on the extended spectral domain approach combined with the mode-matching method, is applied to evaluate the scattering parameter of waveguide discontinuities. The formulation procedure utilizes the biorthogonal relation in the transformation, and the Green's functions in the spectral domain are obtained easily even in the inhomogeneous lossy regions. The present method does not include the approximate perturbational scheme, and it can evaluate accurately and stably the scattering parameters of either for the thin or thick obstacles made of the wide variety of materials, the lossless dielectrics to highly conductive media, in short computation time. The physical phenomena of transmission through the lossy obstacles are investigated by numerical computations. The results are compared with FEM where FEM computations are feasible, although the FEM computations cannot cover the whole performances of the present method. The good agreement is observed in the corresponding range. The matrix size in this method is smaller than that of other methods. Therefore, the present method is numerically efficient and it would be able to apply for the integrated evaluation of a successive discontinuity. The resonant characteristics of rectangular waveguide cavity are analyzed accurately taking the conductor losses into consideration.