Quarter wavelength open stub band pass filter based on dumbbell annular ring resonator for UWB applications

The main target of this paper is to demonstrate the aptitude of dumbbell annular ring (DAR) resonators to the enhancement on the ultra-wideband (UWB) characteristics in microwave filter, a key aspect to improve the selectivity of lower and upper passband. A particular characteristics of filter configuration is that the selectivity of the band pass filters (BPFs) can be conveniently controlled due to DAR, while the bandwidth is almost same. The BPF are recognized using open circuited stepped impedance stubs (OCSIS). Furthermore, the proposed BPF with DARs has symmetric selectivity (>96 dB/GHz), wide passband (>6 GHz), low insertion loss (<;0.2 dB) and good return loss performance (>17 dB). Moreover, for DAR configuration, the group delay is low (<;0.3 ns) over 95% of the passband which results in compact size. Moreover, the proposed filter has many applications in UWB wireless communications. The frequency responses from two software's are in good agreement with the theoretical data.