Design Of Planar Notch Ultra-wideband Bandpass Filter

This article describes the development path of ultra-wideband wireless communication systems before delving into the existing implementation methodologies of ultra-wideband filters and the research challenges.The key concepts used in the development of UWB filters are addressed,including microwave filter technical characteristics,network theory,design principles,and transmission line theory.Afterward,in view of the current problems of insufficient notch depth,poor out-of-band suppression and small number of notches,through the analysis of the notch generation method,two ultra-wideband filters with notch characteristics are designed using the DGS structure.(1)An ultra-wideband filter based on new defective ground structure and loading branches is aimed to address the problems of insufficient notch depth and upper sideband suppression in typical ultra-wideband filters.Double-notch bands are created by embedding and folding open branches in this structure,and asymmetric inverted-T branches are loaded at both ends of the filter to assure notch depth.Etching the specified defective ground structure improves upper sideband suppression and notch depth.The filter works in a range from 2.8 GHz to 11.4 GHz,with a low insertion loss.A depth of 18 d B at 5.3 GHz,and a notch depth and upper sideband suppression of 57 d B at 8 GHz.(2)The issue of ultra-wideband filters having insufficient number of notches and depth of notches is addressed.A microstrip ultra-wideband filter with three notches and enhanced selectivity is presented using a new upgraded multimode resonator and a defective ground structure.The resonator loads branches on both sides and underneath the stepped impedance resonator,builds the ultra-wideband filter’s passband and two notches,and develops the defective grounding structure to enhance the notch and improve the notch characteristics.The filter works in a range from 2.8 GHz to 10.6 GHz,and three notches are generated at 3.8 GHz,5.9 GHz,and8.2 GHz,with a depth of-20 d B between them.It suppresses numerous narrowband frequencies better and is appropriate for circuit integration.It is confirmed by two designs that the DGS structure can deepen the notch depth,improve the out-of-band rejection and increase the notch band.The UWB filter is modeled,simulated and fabricated by the electromagnetic simulation software HFSS,and the accuracy and achievability of the adopted design method are confirmed.The paper has 47 figures,4 tables and 80 references.