Compact Differential Bandpass Filter Using Half-Cut Dual-Mode Dielectric Resonator

This paper presents a design method for differential bandpass filter (BPF) using half-cut dual-mode dielectric resonator (DR). The half-cut dual-mode DR covered by a metal plate on the top surface consists of two identical rectangular DRs in cross-shaped configuration. The metal plate approximately functions as an electric wall, which can be used to realize miniaturization. Meanwhile, it allows a pair of orthogonal half-TE11d modes, which can be differentially excited and coupled by introducing proper perturbation for constructing a differential-mode (DM) passband. To validate the proposed idea, a compact differential BPF is designed, fabricated and measured. Finally, the measured results are very close to the simulation.