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Study On Comparison Design Method And Applications Of Microwave Filters For Wireless Communication

Posted on:2009-10-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:B WuFull Text:PDF
GTID:1118360272465561Subject:Electromagnetic field and microwave technology
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With the phenomenal development in the communication industry, wireless communication has become one of the most popular technologies in this century. And new wireless communication systems emerge ceaselessly, such as GPS, 3G, WLAN, UWB and so on, which have spurred a tremendous advance in microwave active and passive devices especially for filter technology, also make a demand of more stringent filter characteristics. The research work presented in this dissertation focuses on several novel microwave filter structures and their comparison design methods in wireless communication. Novel structures such as coaxial tubular structure, substrate integrated waveguide structure and defected split-ring resonator structure, are applied to the microwave filter design making use of the comparison design method, which includes curve-fitting comparison, structure mapping comparison, complementary element comparison, circuit mapping comparison and so on. The primary work is concluded as follows:(1) The synthesis thoeries of three different types of tubular filters are presented and derived in detail. According to the curve-fitting comparison method between circuit simulation and EM simulation results, the mapping relationship between element dimension and its equivalent circuit is obtained. To simplify the design procedure of the practical tubular filter, section-circuit technology is proposed to realize the structure of tubular filter step by step. By making use of impedance matching to each tubular filtering channel with a certain length of coaxial transmission line, the design problem of non-adjacent wideband tubular deplexer is solved expediently.(2) The structure mapping comparison is applied to build the relationship of element dimensions between rectangular waveguide (RW) filter and substate integrated waveguide (SIW) filter. Based on the existing dimension of the rectangular waveguide filter, making use of the above mapping relation for the same design goal, we can obtain the corresponding dimension of the SIW filter directly. The proposed method has found its application in the physical realization of C-band inductive iris SIW filter, K-band inductive metal hole SIW filter and X-band E-plane metal slat SIW filter.(3) Through the comparison of band-gap properties between microstrip split-ring resonator and split-ring resonator defected ground structure(SRR DGS), it is found that the latter has a flat low pass-band and sharp band-gap characteristic. In virtue of the curve-fitting technology for parameter extracting, the corresponding relation between the element dimension of SRR DGS and its equivalent circuit values is analyzed carefully. In order to improve the out-of-band suppression of the SRR DGS lowpass filter, some effective methods are explored such as loading capacitive stubs on the conductor line and arranging the unit structure periodically. Furthermore, two kinds of SRR DGS bandpass filters with a finite transmission zero are well constructed utilizing the band-gap property of SRR DGS.(4) The resonant and coupling properties of microstrip split-ring resonator (MSRR) and defected split-ring resonator (DSRR) are studied in comparison. The DSRR element shows a similar resonant law and stronger coupling efficients with relative to the MSRR element. Making use of the common feed line structure, two novel defected stepped impedance resonator (SIR) dual-band filters, one is the parallel type and the other is the nested type, are analyzed and designed separately. Incorporating the defected SIR and the microstrip SIR, various kinds of compact and elegancy planar multi-band filters can be realized.(5) Considering the very similar circuit topology of the split-ring resonator defected ground structure (SRR DGS) unit in comparison with the conventional composite right/left handed (CRLH) transmission line, we make a comparing and extending to their circuit models. Then the transmission property, dispersion relation, refraction index as well as impedance characteristic of this SRR DGS unit are derived in detail. The numerical and measurement results validate that, the SRR DGS unit can be regarded as a novel CRLH transmission line unit with a transmission zero. The effect of element number on the transmission property of the periodic structure is discussed, then the design methods of an ultra-wideband filter and a dual-band filter based on such a novel CRLH transmssion line are elementary presented and studied.
Keywords/Search Tags:Wireless Communication, Microwave Filter, Comparison Design Method, Curve-fitting, Space Mapping, Tubular Filter, Substrate Integrated Waveguide(SIW), Split-ring Resonator (SRR), Defected Ground Structure (DGS)
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