A Miniaturized Dual-Mode Cavity Filter Based on Effective Localized Surface Plasmons

Effective localized surface plasmons (ELSPs) are localized surface modes tightly bounded on the surface between two positive dielectrics induced by structural dispersion. The resonance frequency of the dipolar mode was demonstrated to be independent of the radius of the resonator, offering us an effective route in miniaturization of microwave resonators and filters. In this paper, we modeled theoretically and demonstrated a dual-mode cavity filter based on the concept of ELSPs. This filter is constructed by an 18mm × 18mm × 18mm cube cavity and a cylindrical ELSPs resonator with two standard SMA coaxial lines being the input and output ports. Two orthogonal modes are coupled through a tunable screw. The proposed filter works at the center frequency of 2.6GHz with 10MHz bandwidth. Simulation results show that the insertion loss and return loss is lower than 0.5dB and larger than 20dB, respectively. Due to the insensitivity of the resonant frequency to the resonator diameter, this ELSPs-based dual-mode cavity filter only occupy less than half the volume of conventional dual-mode cavity filters with the same design specifications.