Design of monoblock dielectric filter using (PbCa)(FeNbSn)O-3 ceramics

Abstract

The microwave dielectric properties of (Pb1-xCax){(Fe0.5Nb0.5)(1-y)Sn-y}O-3 ceramics (0.4 less than or equal to x less than or equal to 0.6, y = 0.05, 0.1) and design of 900 MHz band 2-pole monoblock band pass filter (BPF) have been investigated to fabricate BPF. Single-phase specimens having orthorhombic perovskite structure similar to CaTiO3 could be obtained in the compositions of (Pb1-xCax){(Fe0.5Nb0.5)(1-y)Sn-y}O-3 (0.4 less than or equal to x less than or equal to 0.6, y = 0.05, 0.1). The substitution of Sn for (Fe0.5Nb0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (epsilon(r)). The temperature coefficient of the resonant frequency of 0 ppm degrees C-1 was realized at x = 0.55 and y = 0.1. The Q.f(0) value and epsilon(r) for this composition were found to be 8600 GHz and 86, respectively. A monoblock lambda/4 dielectric BPF for 900 MHz band portable telephone terminal is presented. This BPF is a kind of combline filter. Computer-aided design (CAD) was used in the modeling procedure. The equivalent circuit of the monoblock BPF is represented by transmission lines and lumped elements based on Z(oe) and Z(oo). A BPF model was designed for surface mounted device (SMD) types. The simulations of the equivalent circuit and BPF structure have been performed to optimize the filter design. Newly developed (Pb0.45Ca0.55){(Fe0.5Nb0.5)(0.9)Sn-0.1}O-3 dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation.