Research On Miniaturized Multi-Function Radio Frequency Filtering Circuits

Filtering circuits are important components in microwave and millimeter-wave(MMW)wireless systems.In classical radio frequency(RF)front-ends,filters are usually cascaded with other circuits,suffering from large sizes,high losses,and the interstage impedance mismatch.To solve these problems,multi-functional circuits by co-designs of multiple circuits are presented by national and international researchers.However,most of the designs operate at microwave frequencies using the planar PCB technology with low Q factors.The design theories and methods cannot meet the requirements of low-loss applications and the MMW wireless applications in B5G/6G.Therefore,this thesis focuses on the researches of miniaturized multi-function filtering circuits,including the designs of passive and active circuits.For the passive designs,single-and dual-channel multi-function filtering circuits based on reusing the resonator are proposed.The substrate integrated waveguide(SIW)and dielectric resonator filtering power splitter/combiners are realized.For the active designs,multi-function filtering circuits based on impedance control are proposed.The microwave multi-function filtering switch circuits based on coaxial resonators and MMW filtering circuits in receiver in CMOS technology are realized.The specific research results are as follows:1.Design methods of filtering power divider/combiner circuits by reusing resonators are proposed to reduce the sizes and loss.Using the electromagnetic field characteristics of SIW orthogonal degenerate mode,the circuit topology of the rat-race coupler is constructed then the co-design of the filter and the rat-race coupler is realized,resulting in size reduction.Based on the multi-mode dielectric resonator,a design method of the filtering power divider in a single cavity structure is proposed.A miniaturized balanced filtering power divider with an arbitrary power division ratio in a certain range is realized by analyzing the coupling matrix to control the impedance.Related research results have been published in the journals of IEEE Transactions on Microwave Theory and Techniques and IEEE Transactions on Circuits and Systems II:Express Briefs.2.Design theories and methods of dual-channel multifunctional filtering circuits are proposed to realize miniaturization and high integration of two multi-function circuits.Based on the orthogonal characteristics of the resonant modes in the SIW,two filter circuits are integrated by sharing the resonator to reduce the sizes.In addition,by using a quad-mode dielectric resonator to construct two filtering channels as well as using the hybrid coaxial resonators and dielectric resonators to integrate the power divider and balun functions,a high-integration dual-channel balanced filtering power divider is designed.Related research results have been published in IEEE Transactions on Industrial Electronics.3.Design methods of multifunctional filtering switch circuits based on impedance control are proposed to reduce circuit sizes and overall losses.By loading the switching circuits to the coaxial filter structure,filter switches based on impedance control are designed.The on-state loss is reduced,the linearity is improved,and the off-state isolation is enhanced.Besides,a novel function reconfigurable filtering circuit model is proposed.The circuit can be reconfigured between an SPQT filtering switch and a four-way filtering power divider without using additional switchable impedance match networks.Circuit complexity and loss are reduced.Related research results have been published in IEEE Transactions on Microwave Theory and Techniques and won a Best Student Paper Award in 2019 International Conference on Microwave and Millimeter Wave Technology.4.Design methods of MMW filtering receiving circuits based on impedance control are proposed,which can be used to suppress the interference of image band in a down conversion receiver and other wireless frequency bands,such as the satellite communication and radar.A compact mixed magnetic-electric coupling circuit is proposed,which can realize the impedance conversion and generate a transmission zero for out-of-band interference suppression.Based on the 28-nm Bulk CMOS technology,a miniaturized filtering low noise amplifier(LNA)and a filtering switch are designed.The fabricated filtering LNA operates at 24-35 GHz,which has a low noise figure(NF)of 2.4-3.6 d B,a maximum gain of 22 d B,and the out-of-band suppression of better than 25 d Bc below 18 GHz.The core circuit size is 0.40×0.33 mm~2.The proposed filtering switch shows the rejection of better than 12.9 d B below 16 GHz.The core circuit has a very compact size of 156×162μm~2.In this thesis,the design theories and methods of high-Q multifunctional microwave filtering circuits are proposed,which show the advantages of miniaturization and integration.The design theories and methods of MMW filtering circuits are also proposed,which can meet the high-performance MMW integrated circuits in the new generation of wireless communication,showing good potential in practical applications.