A very small dielectric planar filter for portable telephones

A high-performance dielectric filter 4.5 mm*3.2 mm*2.0 mm in size has been developed. It has two planar resonators and is made of high-permittivity multilayer ceramic in the Bi-Ca-Nb-O system. The transmission characteristic of the planar filter is found to have a distinctive attenuation pole feature. The behavior of the attenuation pole is explained by the relation between even-odd mode impedances and an equivalent expression with lumped elements.<<ETX>>