Research On High Selective Cavity Multiplexer Technology

With the rapid development of modern wireless communication technology,people's requirements for various indicators of wireless communication system are increasing day by day.Multiplexer plays an important role in the performance of wireless systems.With the increasing shortage of spectrum resources,multiplexers with high selectivity and low insertion loss are attracting more and more attention.Among all kinds of multiplexers,cavity multiplexer has excellent characteristics such as low insertion loss and high power capacity,and has broad application prospects.Firstly,the theory and method of cavity filter and cavity multiplexer are introduced.The basic principle of filter design is given.Waveguide filter and coaxial cavity filter are introduced.Cavity filters and coupling structures with various structures are analyzed.Then,waveguide filters and coaxial cavity filters are designed and discussed.The coaxial cavity filter is chosen to design the cavity multiplexer.The coaxial cavity filter is designed by coupling principle.The coupling theory and various coupling structures are analyzed.According to the need of multiplexer design,direct coupling coaxial filter and cross coupling coaxial filter are designed.Finally,on the basis of coaxial cavity filter,the quadruplexer based on multi-branch structure,the triplexer based on Star junction structure and the quadruplexer based on common cavity structure are designed.Because the frequency band gap of the cavity multiplexer designed in this paper is wide and the phase and harmonics have great influence on the multiplexer,the SIR coaxial cavity is used to change the frequency of the higher harmonics.At the same time,the transmission line impedance is changed to realize perturbation reflection and reduce the influence of phase on the cavity multiplexer.Finally,the processing test of chain structure quadruplexer is carried out.The bandwidth of each passband is more than 400 MHz,the insertion loss is less than 0.9 dB,and the echo loss is more than 20 dB.The performance of the quadruplexer is good.