Research On Shielded Asymmetric Coplanar Stripline As Well As Its Transition And Filter Circuits

Electromagnetic waves can be guided in circuits and be radiated into free space by antennas.Microwave transmission lines are used to guide microwave energy and signals.Microwave integrated circuits(MIC)mainly consist of microwave transmission lines and microwave passive as well as active components.No matter the hybrid microwave integrated circuits(HMIC)and the monolithic microwave integrated circuits(MMIC),microwave transmission lines are always needed.Hence,microwave transmission lines are the foundations for microwave integrated circuits and systems.The metal waveguides and coaxial lines have three-dimensional structure and belong to the first generation of microwave transmission lines.The metal waveguides include the rectangular waveguides and the circular waveguides which have the advantages of low insertion losses,large power capability and firm structure,but bulky,large sizes and adverse to the miniaturization and integration of circuits.The coaxial lines can support the TEM mode and have a wide working frequency band and low instertion losses,but it is difficult to design microwave components using coaxial lines.In 1950 s,the creation of the strip line and the microstrip line leads to the microwave printed circuits(MPC)and the microwave integrated circuits.The strip line,microstrip line,slot line,coplanar waveguide,coplanar stripline,substrate integrated waveguide and composite right/left-handed transmission line belong to the planar microwave transmission line,while finline belongs to the quasi-planar microwave transmission line.The planar and quasi-planar microwave transmission lines are collectively called microwave integrated transmission lines and belong to the second generation of microwave transmission lines.Shielding the asymmetrical coplanar stripline with a metal rectangular waveguide and connecting the ground plate of the asymmetrical coplanar stripline with the metal wall of the rectangular waveguide and then forms a new quasi-planar microwave integrated transmission line,which is called the shielded asymmetrical coplanar stripline(SACPS).The main contents of this dissertation are given as follows:1.Quasi-static analysis of microwave transmission lines using the conformal mapping method.The quasi-static analysis of the finite-boundary multilayer dielectrics asymmetrical coplanar stripline,the multilayer dielectrics filled coaxial line and the conductor-backed connected-ground coplanar waveguide has been implemented by using the conformal mapping method,and the analytical solutions of electrical parameters such as the characteristic impedance and the relative effective permittivity have been obtained.The calculated results of the given analytical solutions and the three dimensional electromagnetic simulation software HFSS have excellent consistency and hence verify the accuracy of the given analytical solutions.2.Structures and characteristics of SACPS and its quasi-static analysis.The SACPS is proposed for the first time.The quasi-static analysis of the SACPS is implemented by using the conformal mapping and the analytical solutions of electrical parameters such as the characteristic impedance and the relative effective permittivity have been obtained.Differences between results of the given analytical solutions and the HFSS software are less than 6% and 3% for the relative effective permittivity and the characteristic impedance,respectively.Compared to the numerical solutions,the given analytical solutions of the SACPS have the advantages of accurate and fast,which can be used to the computer aided design of the SACPS.The SACPS can support the quasi-TEM mode,easy for surface mounting of active and passive components in series or shunt,no need for vias,no radiation,and well suited for millimeter wave integrated circuits and systems.3.Research on the transition circuits for the SACPS.The transition circuits are interfaces for applications of the SACPS.At first,the U band transition circuits from the SACPS to the metal rectangular waveguide are designed,which include the finline type and the probe type.For the complete back-to-back finline type and probe type transition circuits at the whole U band,the measured insertion losses are less than 0.9 and 0.7 dB,respectively,while the return losses are larger than 15 and 10 dB,respectively.Then,a U band transition circuit from the SACPS to the finline is designed.For the convenience of measurement,the finline to rectangular waveguide transition circuit is added.For the complete back-to-back SACPS to finline and to rectangular waveguide transition circuit at the whole U band,the measured insertion losses are less than 1.5 dB,while the return losses are larger than 14 dB.Finally,a W band transition circuit from the SACPS to the microstrip line and an ultra-wide band transition circuit from the SACPS to the microstrip line are designed.All the designed transition circuits are fabricated and tested.The simulated and measured results are good and have high consistency.4.Fundamentals of the microstrip line resonators and its applications in microwave circuits.Microwave resonators are foundations of many microwave circuits such as microwave filters,diplexers and filtering power dividers.Focusing on the microstrip line resonators,the working mechanism of single-mode,dual-mode and multi-mode microstrip line resonators are explained.Then,the research on applications of microstrip line resonators in microwave circuits is taken and microwave bandpass and lowpass filters,two-channel,four-channel and six-channel diplexers as well as single-band and dual-band filtering power dividers are designed.The research on microstrip line resonators can lay a foundation to the research of SACPS resonators and its filter circuits.All the designed microwave circuits based on the microstrip line resonators are fabricated and measured.The simulated and measured results are good and have excellent consistency.5.Research on the filter circuits using the SACPS.Based on the transition circuits for the SACPS and the research on the microstrip line resonators,the research on applications of the SACPS in filter circuits is taken.A W band two-order bandpass filter,a two-order and a three-order W band bandstop filter using the SACPS are designed.All the designed filter circuits are fabricated and measured.The simulated and measured results are good and agree well.