UWB bandpass filter with dual notched bands based on microstrip to CPW transition

In this paper, highly selective ultra-wideband bandpass filter with dual notched bands is proposed. The proposed filter was designed using microstrip to coplanar waveguide transition structure in order to increase the coupling bandwidth. Also, we used stepped impedance stub loaded resonators since the sharp skirt characteristics at lower and upper stop bands are required. In addition, dual notched bands are implemented by spur lines and U-shaped slot resonator for undesired signal interference avoidance (WLAN signals at 5.8 GHz, satellite communication signals at 8.0 GHz) The proposed filter has the measured return loss less than -10 dB in the passband and the bandwidth of passband of 2.32 GHz ~ 10.68 GHz, and the group delay remained relatively flat and less than 0.5 ns in the passband except for the dual notched bands. The rejection center frequencies are 5.43 GHz and 8.07 GHz.