Research On Compact And High Performance Reconfigurable Diplexer For Wireless Communication

With the rapid development of wireless communication technique,communication systems focus on the trends of miniaturization,multiple services,high speed,and low delay.The development trend will make the allocation of spectrum resources increasingly closer,leading to crowded spectrum and signal interference,thus becomes a challenge for wireless communication.Reconfigurable circuits have gained wide development prospect owing to utilization of resources more efficiently.It is very important to develop a research on reconfigurable diplexer with compact size and high performance.This thesis focuses on the design theory of diplexer,the principals of reconfigurable components,the technique of magnetic coupling for suppressing common mode,and the theory of mixed electromagnetic coupling.Based on the projects the author undertaken during the study for a master degree,the research contents are introduced as follows:Firstly,a co-planar waveguide balanced diplexer applied to the 5G communication is proposed,which is based on the technique of magnetic coupling for suppressing common mode.On the basis of this design,a co-planar waveguide tunable balanced diplexer with high common mode suppression ratio is realized.The diplexers are designed with second order multistage stepped impedance resonators,which can achieve miniaturization and wide stopband simultaneously.Because the co-planar waveguide?CPW?circuit can realize grounding without via holes and is easy to be integrated with lumped elements,application of CPW can simplify processing progress and decrease the insertion loss.A CPW balanced diplexer operating at 3.3-3.6 GHz and 4.8-5.0 GHz for 5G communication with common mode suppression great than 30 dB is presented.The isolation S_dd23d23 of the proposed tunable balanced diplexer is less than-40 dB,the S_cc21c21 and S_cc31c31 are below than-50 dB and-30 dB,respectively.Secondly,a tunable diplexer with frequency and bandwidth independently tuning based on mixed electromagnetic coupling is proposed.The diplexer is designed with 1/4 wavelength resonator.Magnetic coupling is produced by short-circuited stub and electric coupling is created by the coupling of open end.The control principal of total coupling coefficients and locations of transmission zeros is analyzed.Frequency tuning is implemented by loading varactor diodes on the open-circuited end,and bandwidth tuning is realized by loading varactor diodes between resonators.At last,based on the study of stub-loaded square ring resonator,a quad-channel high temperature superconducting diplexer is proposed.Furthermore,the resonant characteristic of stub-loaded square ring resonator with a the center-loaded shorted-circuited stub is studied,a switchable filter with four operation states and a switchable diplexer with nine operation states are proposed.The operation mode can be realized by switching of multi-mode resonator by loading PIN diodes in different position on the resonator.All stopband to passband transformation can be realized by loading PIN diode on the open end of multi-mode resonator.A three modes to four modes resonator transformation can be realized by loading PIN diode on the center of square ring stub of multi-mode resonator.