A controllable compact dual-band bandpass filter using loaded open-loop resonators

Abstract

A compact composite open-loop resonator based dual-band band-pass filter (BPF) with high selectivity is presented. The outer open-loop and inner open-loop are corresponding to the first and second frequency passbands, respectively. The middle ring is used as the couping ring. The analysis of these open-loops has also been performed to indicate the resonance condition of the proposed filter. To demonstrate the proposed concept, the filter is fabricated with a compact size, which is 10.20 mm × 18.32 mm. The microstrip line filter is validated and measured with two passbands centered at f₁ = 3.00 GHz and f₂ = 5.34 GHz. The simulation and measured results are in good agreement.