Miniaturised dual-wideband bandpass filter using novel dual-band coupled-line sections

A novel dual-wideband bandpass filter (BPF) by using the proposed dual-band open stub-loaded coupled-line section is presented. The proposed dual-band BPF has a symmetrical frequency response along the designing frequency f₀, and the transmission zero at f₀ improves the filter band-to-band isolation significantly. As an example, a dual-wideband BPF for 2.4 GHz WLAN and 6.8 GHz RFID applications is designed, fabricated and measured. The fabricated filter has the merits of simple topology, compact size, good return loss, low insertion loss and high isolation. The measurement agrees well with the simulation.