Design of a novel dual-band bandpass filter using microstrip/CPW structure

A novel and compact dual-band bandpass filter (BPF) using microstrip/coplanar waveguide (CPW) composite structure is proposed. At the bottom of substrate material, the two CPW open-circuited resonators are broadside-coupled to the top microstrip transmission lines. The proposed dual-band filter has been simulated, optimized, and the obtained frequency responses demonstrated the filter with a good dual-band property, i.e., first pass-band range from 6.2 GHz to 9 GHz (2.8 GHz for -3 dB bandwidth) with central frequency 7.6 GHz, second pass-band range from 10.8 GHz to 15.4 GHz (4 .6 GHz for -3 dB bandwidth) with central frequency 13.1 GHz, and the isolation between the two passbands of the filter is more than 30 dB near 10 GHz. The maximum insertion loss of the dual-band band-pass filter is 1.2 dB in the 1^st pass-band, 1.5 dB in the 2^nd pass-band, respectively. The minimum reflection loss of the dual-band band-pass filter is 20 dB in the 1^st band-pass filter, 15 dB in the 2^nd band-pass filter, respectively.