BROADBAND BANDPASS FILTER USING OPEN COMPLEMENTARY SPLIT RING RESONATOR BASED ON METAMATERIAL UNIT-CELL CONCEPT

摘要

In this article, a compact, wideband, and sharp rejection response bandpass filter based on metamaterial unit-cell concept is proposed. A series LC resonator using an interdigital capacitor and two meanders is designed, and an open complementary split ring resonator is used to realize the parallel LC resonator. Due to parasitic elements, achieving a pure series LC resonator has some difficulty. However, these parasitic elements can add two resonances more than conventional filters based on the metamaterial unit-cell. A design procedure based on a simple equivalent circuit is introduced. A compact bandpass filter at 1.475 GHz, with 94% fractional bandwidth, and an attenuation slope with 85.98 and 35.628 dB/GHz in the lower and upper transition bands, respectively, is designed and fabricated. The measured results are in good agreement with the full-wave electromagnetic simulations inferred by means of Agilent Momentum. The filter has very small size, that is, 0.341λ_g×0.1033λ_g, where λ_g is the guided wavelength at the filter central frequency.