Compact cascaded quadruplet bandpass filter using artificial magnetic resonators

A compact cascaded quadruplet (CQ) bandpass filter (BPF) using artificial magnetic resonators is proposed in this letter.An artificial magnetic resonator, which has a negative effective permeability at the resonant frequency, consists of a shorted spiral structure. The negative-mu characteristics are extracted from the simulation result of the scattering parameters in a fictitious rectangular waveguide. Compared with the open-loop resonators that are usually used to construct conventional CQ-BPFs, the proposed artificial magnetic resonator achieves about an 80% size reduction ratio. The measured insertion and return losses at a center frequency of 2.14 GHz are approximately 1.83 dB and 21 dB, respectively. The group delay is less than 0.81 ns in the W-CDMA passband. The full-wave simulation results are in good agreement with the measurement results.