For purpose of improving selectivity of the ultra-wideband(UWB)filter and reduce interferences from other wireless communication systems to the ultra-wideband system,an UWB filter with double notching and high selection characteristics was designed,which has a ring-type multi-mode resonator coupled with the input and output feeders to realize a high selection characteristics,and then on this basis,it employs a cascaded C-type resonator to generate two notch points.Making use of HFSS optimize the simulation shows that,the filter transmission band stays at 3.1 GHz to 9.7 GHz,and the relative bandwidth is 103.0％together with a selection factor of 0.89,which effectively improves the filter selection characteristics;in addition,a notching point at 6.86 GHz and 8.15 GHz can be seen respectively to avoid the interference from both X-band communication satellites and C-band ones,which can prove both superiority and practical value of this design.
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