Research On Design Methodologies Of Multi-functional Microwave Circuits

To address the needs of multi-band,wide-band,multi-functional,and high-integration evolution of wireless communication systems,this thesis thoroughly discusses the fundamental theories and techniques of microwave circuits with multi-/broad-band operations and multiple functions.This thesis focuses on the aspect of passive components in microwave circuits.Starting from the gener-alized and universal theories,this thesis proposes a series of generalized circuit models,structures,design theories,and techniques.The work of this thesis specifically includes the following aspects.(1)Two novel multi-band impedance transformers are proposed.For the design of concurrent dual-band power amplifiers and based on a conventional dual-band impedance transformer,generalized design theory for dual-band impe-dance transformation design is derived and proposed;to transform frequency-dependent complex impedances with extreme values,a multi-band impedance transformation structure based on ladder networks and coupled lines is pro-posed.(2)A series of function-integrated power dividers are proposed.Based on the coupled-line structure,a miniaturized power divider with impedance-transformation function is implemented by introducing port-extension lines,which realized 44%size reduction;synthesized by the distributed filtering syn-thesis,a novel impedance-transforming balun with dual-band filtering responses is proposed,the out-of-phase outputs of which are realized by introducing double-sided-parallel-stripline-to-microstrip transitions;a narrow-band(6%)filtering power divider with impedance-transformation,ultra-wideband(200%)isola-tion,and dc-block function is proposed,which is constructed by high-Q stub-loaded coupled lines;embedding transversal signal interference sections in the traditional Wilkinson power divider,a power divider with ultra-wideband(90%)filtering function is designed and implemented;based on coupled lines and vari-able capacitors,a new power divider with tunable bands and complex-impedance transformation is designed and implemented.In this thesis,rigorous and con-cise design theories are deduced,and numerical and experimental verifications are carried out to prove the effectiveness of the design methodologies.(3)A series of multi-/wide-band function-integrated couplers are proposed.By introducing port-extension lines in a coupled-line coupler,an unequal dual-band quadrature coupler is designed and implemented;employing high-Q cross-shaped microwave ceramics,a narrow-band filtering rat-race coupler is con-structed;by introducing coupling feeds to a coupled-line coupler,a wideband(58%)filtering quadrature coupler with unequal power divisions and dc-block function is implemented;based on the conventional branch-line coupler,a uni-versal coupler with optional power divisions,arbitrary phase differences and alternative port impedances are proposed,and the generalized design method-ology is derived;by innovatively introducing tunable phase shifters,a wide-band quadrature and rat-race coupler is proposed,which has the properties of phase-controlled and ultra-wide-range(±25 dB)tunable power divisions.These efforts are devoted to the research of generalized coupler theory and their multi-functional integrations.The experimental verification method is utilized to prove the correctness and effectiveness of the design method.(4)A series of balun-free power dividers and couplers applied in differen-tial and single-ended hybrid systems are proposed.Flexibly applying the short-ended coupled line and its equivalent circuit,a planar balanced-to-unbalanced in-phase power divider with wideband(50%)filtering response and ultra-wideb-and(222%)common-mode rejection is proposed,which addresses three ma-jor pain points of balanced-to-unbalanced power dividers;by introducing full-wavelength lines to conventional branch-line couplers,quadrature and rat-race couplers with balanced and balanced hybrid ports are firstly proposed,which have the properties of optional power divisions,arbitrary terminated resistances;constructed by the nested double-ring structure,a crossover with balanced and single-ended paths is firstly proposed.These hybrid circuits are versatile and feature-rich,have good common-mode interference rejection,and do not re-quire external baluns,making them excellent candidates for building differen-tial and single-ended hybrid systems.These researches have been published in IEEE Transactions on Circuits and Systems Ⅰ:Regular Papers,IEEE Transactions on Microwave Theory and Techniques,IEEE Transactions on Components,Packaging and Manufacturing Technology,IEEE Microwave and Wireless Components Letters,IEEE Access,Electronics Letters,AEU-International Journal of Electronics and Communi-cations,International Journal of Microwave and Wireless Technologies,Mi-crowave and Optical Technology Letters,Electromagnetics,and China Com-munications,and a Chinese patent was granted.