Research And Design Of Miniaturized High Performance Filters With Wide Stopband

The design of traditional planar filters mainly adopts the structures of microstrip line,slot line,coplanar waveguide(CPW),defect ground structure(DGS),etc.,which is difficult to further realize the size miniaturization and performance improvement.At the same time,as an important branch,bandpass filters(BPFs)with wide stopband are paid more and more attention by academia and industry.Therefore,how to use the novel passive circuit structure to achieve high performance and miniaturization BPF with wide stopband remains a great challenge.In this dissertation,a number of wide stopband filters are proposed based on basic theory,analysis methods,and different physical structures of plane filters.The main innovations are shown as follows:Two types of dual-mode hybrid microstrip line/DGS resonators with wide stopband are proposed in this dissertation.It combines the characteristics of microstrip line and DGS,which can realize dual-mode response with wide stopband characteristics in a compact size.The measured results are in close agreement with the simulated ones.These two dual-band BPFs have ultra-wide upper stopband characteristics up to 40 GHz with stopband suppression more than 28 d B.A dual-band filtering power divider(FPD)with wide stopband is proposed.Such FPD is composed of two parts,one is a wide stopband BPF based on hybrid microstrip line/DGS,the other is a microstrip line power divider with high isolation.By cascading the two parts,the FPD can achieve the filtering characteristics with ultra-wide stopband.Meanwhile,the measured results show that the dual-band FPD has more than 18.7 d B inband isolation and more than 28 d B stopband suppression from the upper stopband bandwidth to 40 GHz.Based on substrate-integrated defect ground structure(SIDGS),a high selectivity wide stopband BPF with low radiation loss is proposed.In this filter design,two kinds of SIDGS resonators with inconsistent harmonics are proposed,and the wide stopband response of the filter is realized through the mutual suppression of harmonics of the resonators.In addition,a weak coupling is introduced to generate a transmission zero in the upper band of the filter,which improves the selectivity of the passband.The measured stopband bandwidth was up to 26 GHz,and stopband rejection level is higher than 27 d B.Based on SIDGS and stepped-impedance microstrip line structure,a miniaturized wideband BPF with wide stopband is proposed.The SIDGS can effectively reduce the size of the circuit,and realize the ultra-wide stopband characteristics through the difference of harmonic position with the microstrip line resonator.Besides,the measured results show that the wideband BPF can realize the stopband suppression greater than 20 d B,and the stopband range is up to 20 GHz.A millimeter-wave miniaturized BPF with wide stopband is proposed based on fivelayer printed circuit board(PCB)technology in this dissertation.The BPF adopts a selfpackaging structure,which not only reduces the circuit size and the insertion loss,but also effectively eliminates the electromagnetic radiation effect of the device.Meanwhile,the harmonic suppression of the BPF is more than 24 d B,and the stopband is up to 110 GHz.In conclusion,this dissertation presents various design examples of miniaturized BPF with wide stopband based on hybrid microstrip line/DGS,SIDGS,and self-packaged strip-line.Meanwhile,the design theory and research methods of these BPFs are summarized,which has important reference value.In addition,the proposed BPFs are attractive in wireless communication systems.