Design of monoblock dielectric filter using (PbCa)(FeNbSn)O₃ ceramics

The microwave dielectric properties of (Pb_1-xCa){(Fe_0.5Nb_0.5)_1-y Sn_y}O₃ ceramics (0.4≤×≤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 (Pb_1-xCa_x){(Fe_0.5Nb_0.5)_1-y Sn_y}O₃(0.4≤×≤0.6, y = 0.05, 0.1). The substitution of Sn for (Fe_0.5Nb_0.5) significantly increased the quality factor Q and slightly decreased the dielectric constant (ε_r). The temperature coefficient of the resonant frequency of 0 ppm °C^-1 was realized at x = 0.55 and y = 0.1. The Q·f₀ value and ε_r for this composition were found to be 8600 GHz and 86, respectively. A monoblock λ/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 (Pb_0.45Ca_0.55){(Fe_0.5Nb_0.5)_0.9Sn_{0 .1}}O₃ dielectric materials were used for BPF fabrication. Experimental results of the fabricated device were in good agreement with the simulation.