Compact ultra-wideband bandpass filter using quad-T-stub-loaded ring structure
A compact ultrawideband (UWB) planar bandpass filter (BPF) using quad-T-stub-loaded ring resonator is presented. At this filter, two sets of the four high impedance lines at the two sides of the ring as the coupling fed structure are used to gain much stronger coupling effect. Compared with the conventional ring resonator filter, the bandwidth of the UWB BPF can be improved after we load four T-shaped stubs on the ring resonator. That is because these stubs can increase the effective electrical lengths, and also lower the second and third resonant frequencies of the ring resonator at no expense of the size increase. Finally, a prototype of the proposed UWB BPF with 3 dB fractional bandwidth of 101% has been designed and fabricated. The measured results are in good agreement with the full-wave simulations. © 2014 Wiley Periodicals, Inc.
Xu, KD; Zhang, YH; Li, JLW; Joines, WT; Liu, QH
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