Study On Multi-mode Resonators And Their Application To Filters And Diplexers

As wireless communication technology is developing rapidly,it has penetrated into every field in our lives.Wireless communication technology has brought great convenience to us,but also makes the spectrum resources increasingly tense.Therefore,higher requirements for the performance of microwave devices have been put forward to ease tensions of spectrum resources and ensure the communication quality,which brings greater challenges to RF engineers.As the most important frequency selection devices,microwave filters play a huge role in addressing these issues.The merits of miniaturization,low cost,easy integration,low insertion loss,high selectivity and wide stopband are the goals which the researchers and development personnel pursue.In order to improve the integration and compatibility of wireless communication systems,a variety of multi-band and ultra-wideband filters are constantly being developed.In the design of multi-band and ultra-wideband filters,an effective means to realize miniaturization is to reduce the number of resonators,the dual-mode resonators,tri-mode resonators and even multi-mode resonators contribute to achieving this goal.Multi-mode resonators have more than one independent resonance modes,which can be used to replace two,three and even a plurality of resonators.In addition,multi-mode resonators have the advantage of high performance,low cost and high integration over other common resonators.According to the published papers in related fields,the author proposed several novel multi-mode resonators.Based on these multi-mode resonators,dual-band,tri-band,quad-band and ultra-wide band filters,and a quad-channel diplexer were designed and fabricated in this dissertation,and good results can be observed in each design.The works in this dissertation are summarized as follows:1.The analysis method of general and symmetrical structure multi-mode resonators was systematically studied,based on this,several common basic resonator element and multi-mode resonator were analyzed in detail,and the frequencies formulae were given.The design methods of microware filters and diplexers were systematically studied,and an application for design cross coupling filters were developed based on C#programming language,which laid the theoretical foundation for the follow-up works in this dissertation.2.A novel quad-mode stub-loaded ring resonator was proposed and its resonance characteristics were detailed analyzed by using the even-odd-mode method,then the frequency formula of each resonance mode was derived and the design graphs were given.Based on the proposed quad-mode resonators,two dual-band filters were implemented,which have independently controllable passband frequencies and bandwidths.In the design of the second dual-band filter,source-load coupling was introduced,and more transmission zeros were generated between the two passbands,which greatly improve the isolation level between the passbands.On the basis of the proposed quad-mode resonator,a centrally stub-loaded structure was added to form a hexa-mode combination resonator,Using the hexa-mode resonator,a tri-band filter was designed.Compared to the designed dual-band filter,the tri-band filter has one more passband whereas the circuit size was almost not increased.3.A novel stepped impedance stub-loaded quad-mode resonators was proposed,which has more controllable higher harmonics.Based on it,a dual-band filter was designed and the source-load coupling was introduced to improve the isolation between passbands.The upper stopband was extended up to 4.3 fcl with rejection greater than 20 dB.By adding one/two centrally stub-loaded stepped impedance resonator(s),a hexa-mode and an octa-mode combination resonators were proposed.Based on the proposed combination resonators,a tri-band and a quad-band filter were designed,which verify the performance of the stepped impedance stub-loaded multi-mode resonators.4.A novel stub-loaded multi-mode resonator with symmetrical structure was proposed.Due to its symmetry,even-odd-mode method was utilized to analyze the resonance characteristics in detail.The frequency formula and the design graphs were given.Based on the proposed resonator and by properly tuning each mode frequency,an ultra-wideband filter with FBW of 110%was designed.Interdigital coupling feed lines were properly designed to provide external coupling for each passband.Multi-region DGS was initially adopted to enhance the coupling strength and improve the flatness of the passband.5.Based on the proposed quad-mode resonator,two dual-band filters operating at different frequencies were designed.The matching network was designed to connect the two filters to form a quad-channel diplexer.Only two resonators of one type were applied in this design,which greatly reduce the number of resonators and the circuit size.On some occasions,the designed quad-channel diplexer can be used to replace quadruplexer while the designed quad-channel diplexer has a smaller circuit size,more flexible design procedures.This work will be instructive on the application of multi-mode resonators and multi-band filters to diplexers.