Research On Synthesis And Optimization Of Microwave Multiplexer

Microwave multiplexer is a multi-port passive device with frequency selective function, which is widely used in satellite communications, radar systems, electronic countermeasure, etc. With the rapid development of communication technology, the performance requirements of multiplexers are gradually increased, which increases the design difficulty of multiplexers. Therefore, the researches of microwave multiplexer synthesis and optimization are very important. Aiming at the synthesis and optimization of microwave multiplexers, some researches have been carried out in this thesis.Firstly, the theory of generalized Chebyshev filter synthesis was introduced, which is the foundation of microwave multiplexer theory. And a fourth-order open-loop resonator filter was designed and fabricated, validating the effectiveness of the synthesis approach. Then, the coupling matrix optimization algorithm with user-defined topology was proposed to make the selection of filter topology more flexible.Secondly, the method of microwave multiplexer synthesis was investigated, including the derivation of characteristic polynomials of multiplexer’s scattering parameters, and the derivation of filter’s coupling matrix with interaction of different channels. To simplify the design process, a software for microwave multiplexer synthesis was designed. And an open-loop resonator duplexer was designed and fabricated, the circuit performances were demonstrated to be good.Lastly, an automated optimization algorithm for microwave filters and multiplexers was proposed. In this algorithm, the iterative formula of aggressive space mapping is used as core concept, the Cauchy method is used to extract the equivalent circuit parameters from the electromagnetic simulation results, while the MATLAB scripts is used to control the electromagnetic simulation software to make the optimization procedure automated. To verify the reliability of the automatic optimization algorithm, a coaxial cavity filter and duplexer was designed and simulated, and both achieve good circuit performances after several iterations.The study of microwave multiplexer in this thesis simplifies the multiplexer design process, improves the flexibility of topology selection, and saves the simulation and optimization time, which reveals potentially practical applications in engineering.