Miniaturized Ultra-wideband Filter And Dual-mode Filter Design,

Many new wireless communication systems are proposed and adopted, (such as GSM, WCDMA, WLAN, WIMAX, UWB and so on), making the filter technology research has become a popular direction. The ultra-wideband and dual-passband filter have become research hotspot in recent years because the demand on sufficient usage of frequency spectrum and compatible of different communication system. The research work presented here focuses on ultra-wideband and dual pass-band filter design. Based on the analysis of microstrip structures, such as short-circuited stubs, circular patch resonators and so on, many ultra-wideband and dual-passband filter working at the wireless communication band are designed.The main work in this paper can be summarized as followings:1. A new UWB filter with good passband and stopband performance is designed based on short-circuited stubs structure. The filter is compact and easy to fabrication and the measured results show good agreement with the simulated results.2. Some narrow-band communication systems (eg WLAN) may produce interference in the UWB spectrum. This paper presents a novel UWB filter, with single notch-band or double notch-bands, can eliminate the interference. The UWB filter has good notch-band performance and the notch-band can be adjusted easily. The engineering practicability of this method is approved on the basis of comparing and analyzing the measured results and simulated results.3. The design methods of dual-mode filter are studied. A dual-mode dual-passband filter based on line-ring coupled circular feed patch is designed after some common methods of dual-mode filters were described. The filter is measured and the results show that the filter has a good double-pass band response.4. A novel dual-mode dual-band bandpass filter is proposed and experimentally studied, and the dual-mode dual-band response is realized based on the slits were embedding on the circular patch. Three transmission zeros and each pass-band response has two transmission poles are achieved. The measured results have good agreement with the simulated results. The good passband and stopband characteristics show that the filter has a strong engineering practicality.