Research And Design Of Microstrip Filter Coupler

Microwave directional couplers are important passive components of wireless communication systems.Due to the increasing demands of society and the expectation of wireless communication technology,the research focus of microwave directional couplers has turned to miniaturization,multifunction and reconfigurability.Compared with the traditional coupler,the multifunctional directional coupler has functions such as band-pass filtering in addition to the basic power distribution and phase difference output,which further improves the working quality and practicability of the circuit;Compared with the traditional couplers,the reconfigurable coupler has the advantage that the electrical performance parameters of the circuit can be adjusted in real time.This thesis explores the functional fusion design of filter and coupler based on 3 d B directional coupler.The main content and research value of this work can be summarized in the following two aspects:1.The design method of harmonic suppression coupler with variable phase difference is studied.The basic principle of the design of the variable phase difference in this scheme is expounded,the network analysis and formula derivation of the theoretical circuit model are carried out by the even-odd mode analysis method,and the detailed correlation formula between the phase difference and the basic parameters of the circuit is given;Two kinds of resonator structures are analyzed,and a suitable second harmonic suppression circuit is obtained.Finally,a set of circuit parameters that meet the design goals are comprehensively designed and verified by simulation and machining.The final result reasonably proves the reliability of this design method.2.A band-pass filter coupler structure with adjustable center frequency is proposed,which can not only realize band-pass filter response,but also adjust circuit parameters in real time.By analyzing the equivalent circuit of the proposed circuit structure,the relevant parameters of the filter coupler can be obtained,and then all the basic parameters of the circuit can be synthesized by deriving the formula of the external quality factor and coupling coefficient.Finally,a simulation design example is provided and tested.Compared with similar literatures,the harmonic suppression coupler with variable phase difference proposed in this thesis can not only suppress the second harmonic signal well,but also can change the phase difference arbitrarily.The filter coupler can not only realize the adjustable center frequency,but also reduce the circuit area and circuit insertion loss.This provides a new design method and idea for coupler design with filter response,and provides better circuit performance for wireless communication systems.