Research And Design On Microwave Dual-mode And Hybrid Multimode Bandpass Filter

In recent years, the telecommunications industry to flourish, especially the widespreaduse of WLAN, multi-band communication system which can now also compatible with avariety of communication resources has become a hot topic, and multi-band filter as a keycomponent of the communications front also catch much attention.so, the research of highperformance multi-band microwave filter has important significance. In this paper, the designprinciple of multi-band filter is researched, and designs a variety of multi-band wirelesscommunication system filter. The main work of this paper includes the following threeaspects:The first one is proposed a compact microstrip tri-band bandpass filter (BPF) usingshort-circuited stub-loaded stepped impedance resonator (SIR). The hairpin SIR generates adual-mode dual-band response by loading a short-circuited stub. The nature of the proposedresonator is investigated through the even-odd mode analysis. A pair of extended feedlinesadds a new transmission path to produce the third passband. The proposed SIR and extendedfeedlines are folded and thus cause compact size for the filter. Three passbands are designedto operate at1.57/3.5/5.2GHz, respectively. All the theoretical analysis has been successfullyverified by experiment resultsThe second one is proposed a compact multi-band bandpass filters (BPFs) usingquad-mode stub-loaded resonators. A novel approach about the mode splitting characteristicsof the quadruple-mode resonator is investigated, which can provide dual-band behavior. Aquad-band filter is proposed and designed by cascading two quadruple-mode resonators thatthe upper one operates at1.8/2.4GHz (GSM-and WiMax-band) and the lower one worksat1.57/2.1GHz (GPS-and WCDMA-band). The proposed filters have been fabricated.Good agreement between simulation and measurement verifies the validity of this designmethodology.The third one is proposed a compact dual-band high-temperature superconducting (HTS)hairpin-resonator bandpass filter (BPF) based on a multimode resonator. This multimoderesonator consists of two hairpin resonators loaded with a common T-shaped stub. TheT-shaped stub excites one pair of non-degenerate modes for the inner hairpin resonator whilethe combination of T-shaped stub and the inner hairpin resonator produces another pair ofnon-degenerate modes for the outer hairpin resonator. Moreover, the former generates thehigher passband and the latter produces the lower passband which are controlledindependently by the corresponding hairpin resonator. The proposed dual-band HTS filter wasfabricated and measured. Good agreement between simulation and measurement verifies the validity of this design methodology.