Conductor-Backed CPW Bandpass Filters With Electromagnetic Couplings

High selective bandpass filters (BPFs) using end-connected conductor-backed coplanar waveguide (CBCPW) have been proposed, and the electromagnetic (EM) couplings have been investigated. Filter transmission zeros (TZs) are attributed to the separated electric and magnetic coupling paths, and the additional coupling resonators are not desired. Either magnetic-dominant coupling or electric-dominant coupling generates a TZ but at the different sides of the passband. The proposed dual-band CBCPW BPF has been fabricated and measured. The experimental results demonstrate the new design. The advantages of the CBCPW BPFs are not only their simple and compact circuit topologies, independently controllable TZs and center frequencies, but also the less EM waves leakage which are due to the EM shielding.