Simplified analysis of inhomogeneous dielectric block combline filters

Dielectric block combline filters constructed of low-loss temperature stable high dielectric constant ceramic materials are used in very large quantities for mobile communications. An inhomogeneous version having significant advantages in terms of achievable Q factor and symmetry of response characteristics was introduced by A. Fukasawa (1982). An analysis of this structure which clearly depicts its novel aspects by giving a physically significant equivalent circuit is presented. A simple theory for combline filters have full quarter-wavelength resonators is outlined. In addition to improved understanding, the simplification could lead to wider utilization of such inhomogeneous structures and stimulate advances in the technology.<
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