Research On Key Technologies Of Microwave And Millimeter-Wave Front-End Passive Circuits

Today,various communication systems and standards will co-exist and accommodate each other with the diversified development of communication standards.As a key component in the front-end of communication systems,the traditional front-end passive circuit with complex structure,large size and single function can no longer satisfy the development needs of communication systems.In response to the application requirements of microwave millimeter wave system front-end,the thesis proceeds with the study of key technologies for front-end passive circuits.The main research work includes the following.1.A new microstrip-probe isolation circuit for waveguide power divider is proposed,and a Ka-band Gysel power divider with wide isolation bandwidth is designed in this thesis.The new microstrip-probe isolation circuit is composed of a microstrip probe and a microstrip line with two resistors.Compared with the traditional isolation circuit,the new isolation circuit can provide a wider isolation bandwidth.2.An isolation circuit without isolation resistance based on the lossy LC resonant network is proposed,and a millimeter-wave high-isolation four-way power divider with double-layer dielectric substrate is designed in this thesis.The upper microstrip circuit dielectric substrate is made of low-loss material,which is used to realize the function of equal power distribution,ensuring that the power divider has the advantages of low loss and good input impedance matching.The lower microstrip circuit dielectric substrate is made of high-loss material,which is used to realize the isolation function between the output ports.A lossy LC resonant network is used instead of the traditional isolation resistor to ensure that the power divider has the advantages of high isolation and good output matching.3.A compact filtered matching load based on lossy interdigital filter is proposed in this thesis.The lossy interdigital filter is composed of a plurality of quarter-wavelength microstrip resonators coupled in parallel,where one end of the resonator is open-circuited and the other end is short-circuited.The input and output ports of the lossy interdigital filter are magnetically coupled with the microstrip resonator by means of taps.The compact filtered matching load is achieved by cascading multiple lossy interdigital filters and shorting/opening circuit at the terminal.4.A triplexer based public cavity with high selectivity is designed in this thesis,which mainly consists of several coaxial cavity filters.According to the coupling principle,the coaxial cavity bandpass filters are designed.Three coaxial cavity bandpass filters are combined through a non-resonant public cavity structure.The public cavity is set to ensure that each passband is well matched and has good isolation at the same time.