UWB waveguide bandpass filter with two ultra narrow notched bands

A compact ultra-wideband (UWB) bandpass filter (BPF) with two notched bands based on ridged waveguide is presented. Capacitive loading short stub structures are introduced to reject the undesired wireless local-area network (WLAN) radio signals (i.e., 5.2-and-5.8-GHz bands). By independently adjusting the heights of the capacitive loading posts in the short stubs, the centre frequencies of two notched bands can be allocated at 5.2 and 5.8 GHz, while the bandpass is almost not affected. A UWB BPF has been simulated, fabricated and measured, with good agreement between the simulated and measured results. Good passband and stopband performances are achieved. Specifically, the two notched bands centered at 5.2 and 5.8 GHz have 10 dB rejection fractional bandwidths of about 2.3% and 2.06%, respectively.