Compact multilayer dual-band and tri-band bandpass filters using grounded spiral resonators

Abstract

In this paper, a compact multilayer dual-band and tri-band filters based on grounded spiral resonators are proposed. The filters are realized on two stacked substrates: Taconic CeR-10 substrate and Kapton foil, where the feeds are positioned in the upper layer whereas resonators are placed in the middle layer between feed lines and the ground. The proposed dual-band filter operates at 0.68/0.82 GHz while tri-band filter, realized using addition quarter-wavelength resonators, operates at 0.634/0.81/1.1 GHz. Specific geometrical arrangement of the resonators result in three transmission zeros providing high selectivity of the passbands and high suppression out of the passband up to the second harmonics.