Research Of The Circuits Formed By Multi-resonant-mode Couplings Based On Coupled-mode Theory

Filter and circulator are important parts of microwave communication system,and they are widely used in wireless communication base station and terminal products.For the first time,the coupling-mode theory in optics is integrated into the microwave circuit design based on multi-mode resonant coupling.The microstrip bandpass filter and the active three-port circulator are designed respectively.First,the coupling of N-mode resonant is deduced in detail,and a design method for N-order passive filter is realized.The method includes analytic computation,eigenmode simulation and optimization.The loss item is successfully introduced into the analytical calculation,which realizes a good agreement of frequency response between the theoretical calculation and the simulation result.The method greatly improves the design speed and precision of the filter.Based on this method,several microstrip bandpass filters with high out-band suppression were designed.It includes second-/third-order filters designed use GaAs substrate,and third-order filters designed based on PCB materials.Simulation and optimization of the designed filters are carried out using the three-dimensional electromagnetic simulation software HFSS and the RF circuit design and simulation software ADS.The filters are fabricated and tested,the test results are in good agreement with the theoretical simulation results.In addition,the design of the on-chip integrated nonreciprocal device is accomplished based on the coupled-mode theory.A microwave active three-port circulator is developed for the continuous wave transceiver radar system.Board-level and chip-level active circulators are designed and simulated.The simulation results show that the circulators have good performance of transmission and isolation.The design method of the circulator has great significance for realizing the chip-making of traditional nonreciprocal microwave device and realizing the development of single-chip integrated with the front-end microwave circuit of the system.Finally,we summarize and prospect the problems which may be able to be improved in the research.