Sanyo Electric Co., Ltd.

Yasuhiko Okamoto

Kenichi Shibata

Kenichi Ezaki

Kazuhiko Kuroki

Hisakazu Takahashi

Yoko Baba

Atsushi Ito

Shigeyuki Yasuyama

Coaxial resonators serving as input and output stages are arranged on a dielectric substrate having input and output coupling strip lines and a grounding electrode formed in the same plane as the strip lines and surrounding the strip lines. The substrate is shaped substantially in conformity with the bottom contour of the resonators as arranged on the substrate.

Dielectric filters and duplexers incorporating same

A microwave ceramic composition containing as main components substances expressed by a composition formula of x.BaO - y TiO.sub.2 - z.Nd.sub.2 O.sub.3 (where 0.05&lt;=x&lt;=0.25, 0.60&lt;=y&lt;=0.85, and 0.05&lt;=z&lt;=0.225) when their molar fractions are taken as x, y and z (x+y+z=1) and containing as a subcomponent one type selected from the group consisting of In.sub.2 O.sub.3, Bi.sub.2 O.sub.5, GeO.sub.2 and V.sub.2 O.sub.5.

Microwave dielectric ceramic composition

A microwave dielectric ceramic composition which is obtained by selecting, in a composition formula of (A.sup.1+.sub.1/2 .multidot.B.sup.3+.sub.1/2) TiO.sub.3, Li.sup.1+ and Nd.sup.3+, Co.sup.3+ or Pr.sup.3+ as A.sup.1+ and B.sup.3+, respectively. The dielectric ceramic composition expressed by (A.sup.1+.sub.1/2 .multidot.B.sup.3+.sub.1/2) TiO.sub.3 has a high dielectric constant and has a temperature coefficient of resonance frequency .tau.f which is large on the minus side. MgO, CoO, ZnO, CaCO.sub.3 or SrCO.sub.3 is added to such a dielectric ceramic composition expressed by (A.sup.1+.sub.1/2 .multidot.B.sup.3+.sub.1/2 /TiO.sub.3, to improve the Q value of the dielectric ceramic composition.

A microwave dielectric ceramic composition containing as main components substances expressed by a composition formula of x.multidot.TiO.sub.2 -y.multidot.ZrO.sub.2 -z.multidot.SnO.sub.2 (where 0.30.ltoreq.x.ltoreq.0.60, 0.25.ltoreq.y.ltoreq.0.60, and 0.025.ltoreq.z.ltoreq.0.20) when their molar fractions are taken as x, y and z (x+y+z=1), and containing as additives predetermined amounts of one type selected from the group consisting of MnO, Al.sub.2 O.sub.3, CuO, Li.sub.2 O and Ga.sub.2 O.sub.3 and predetermined amounts of one type selected from the group consisting of Nb.sub.2 O.sub.5 and Ta.sub.2 O.sub.5.

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Osaka, Japan

Yasuhiko Okamoto