Filtering Devices Research Based On Microwave Resonance And Coupling Theory

Multi-function,integration and miniaturization are the development trend of wireless communication system,which also puts forward the same requirements for a series of basic components of RF microwave system,such as filter,antenna,matching circuit,etc.The traditional design of antenna,amplifier and other devices often needs specific analysis for different specific problems.The design process is diverse,but the scope of application has obvious limitations,which often depends on the subjective experience of designers.As a result,for the same specification,products designed by different designers may have big differences in complexity,cost,reliability and performance.Especially in the multifunctional,integrated and miniaturized device design,the traditional design method is more incompetent in the trade-off process of multi-functional and size factors.In essence,a large number of RF microwave device functions are realized by using resonance and the coupling effect between multiple resonance modes in various ways,so that the performance of the device,such as port reflection characteristics,transmission characteristics and radiation characteristics,can meet the expected requirements within the required frequency range.In addition to the design of filters,there is not a highly unified rigorous method for the design of other devices.Similarly,microwave filter is based on the resonance coupling principle.For microwave filter,a rigorous,mature and effective coupling matrix theory based on the coupling resonance principle has been developed.At present,this theory is mainly used for filter design.But the coupling resonance principle contained in it is widely used in various types of microwave devices.Coupling and resonance is the basic essence of most microwave RF devices to work normally.Based on the analysis and control of coupling and resonance phenomenon in the current mature filter design theory.This paper studies the microwave RF devices such as resonance structure,amplifier and antenna from the perspective of resonance coupling principle,which provides some new ideas for the integration of various traditional device functions and filtering functions as well as the unification of design process.The main contents of this paper are as follows:1.In order to solve the problem that only a few data points are used in the current quality factor(Q value)extraction method,which may result in large errors,and some methods are inconvenient to operate.A resonator Q value estimation method based on least square estimate(LSE)is proposed.The Q value and other equivalent parameters of resonance structure or circuit with additional loaded phase are extracted in two steps.First,the loaded phase is de embedded by using LSE,and then other parameters are extracted by using LSE again.Then the proposed method is used to extract four resonators.The results are compared with the software QZERO which is considered to be the standard in the field,which fully proves the accuracy and convenience of the proposed method.It lays an important foundation for the subsequent design of other devices based on resonance and coupling.2.The traditional RF front-end uses a cascade of amplifiers and filters,which will take up a large size and bring loss.A filtering amplifier is designed,which works at 5.6 GHz ~ 5.9 GHz,and has the function of filtering and amplifying.By modifying the external coupling parameters of the filter slightly,it can be directly used to replace the traditional amplifier matching network.The simulation results show that with the circuit size changes little,it not only realizes the impedance matching function,but also has superior filtering characteristics,which achieves the purpose of the integrated design of the signal filtering and amplification functions.3.The most used schemes for filtering antennas include cascade,co-design and series-fed array scheme.But there are disadvantages of high loss,inflexibility and uncontrollability of radiation nulls for those schemes.A synthesis and design method of general filter antenna based on parallel structure is proposed.The antenna with filtering characteristics can be realized by using several common resonant antennas as the resonator elements and radiating energy to the space at the same time.Given the filtering performance specification,the resonant frequencies and radiation quality factors of each element can be synthesized by the coupling matrix synthesis theory or other methods.The working principle of the proposed filtering antenna is analyzed in detail from the point of view of field and circuit.In this method,different number of elements can be used according to different specifications.And the required passband and position of radiation nulls can be achieved by coupling matrix synthesis.Then a filter antenna with a passband of 5.71 GHz to 5.85 GHz and a radiation null at 5.6 GHz is designed using rectangular patch resonant antenna elements.The process of structure realization based on the proposed design method is introduced in detail,including the steps of dimension determination,the influence of the separation between elements and feed network design.The final calculated,simulated and measured results verify the feasibility and generality of the proposed method.