Research Of Power And Mode Measurement Of W-band High-ordered Overmoded Waveguide

In an Expanded Interaction Oscillator(hereinafter referred to as EIO),the waveguide structure involved is mainly a circular waveguide(there are also rectangular waveguides,etc.),especially its output port.The work in this paper is carried out in the background of the EIO designed by our team,which works in the W-band,and needs to measure its power through a directional coupler composed of an overmodulated circular waveguide and a standard rectangular waveguide at the output port.Not only that,for the output wave of the overmode waveguide,in addition to measuring its power,it is also necessary to analyze its output mode.There are two measurement methods selected in this paper.One is to realize power measurement and mode analysis at the same time through the waveguide directional coupler,that is,to realize the analysis and research of different modes through the difference in the coupling degree of different modes in the overmode waveguide.One is to study the output port medium of the device through thermal analysis,and determine the field distribution through its temperature distribution,and then determine the mode category.First,a circular waveguide-rectangular waveguide directional coupler with high directivity is designed to realize power measurement.As a commonly used microwave component,the directional coupler plays an important role in microwave systems such as signal generation and receiving devices.The main design index of the directional coupler designed in this paper is that the coupling-frequency curve of the coupler should be as flat as possible,the frequency band should be as wide as possible,the directivity should be as wide as possible,and the mode interference should be reduced as much as possible,so as to improve the measurement accuracy.Therefore,a comprehensive and systematic research on the circular waveguide-rectangular waveguide directional coupler not only has certain theoretical significance,but also has important application value.Secondly,this paper designs another directional coupler based on magnetic coupling to distinguish the main higher-order mode and the main mode in the overmode circular waveguide.The device is designed based on parameters such as electric field distribution,power decibel,and wall current distribution of each mode.It has been proved by research that it has good coupling isolation between the main mode and the three main modes,and these modes can be separately Analysis and Measurement.Finally,through the combination of the directional coupler method and the temperature analysis method,the measurement of the main mode and the high-order mode which is the main component in the overmode waveguide is realized more accurately.This part of the work is mainly based on two aspects.One is to consider the needs of mode analysis in the design of the directional coupler,so that the coupling degree corresponding to different modes will be different by changing the coupling structure during design,and the mode can be achieved.The purpose of selection;the second is to conduct simultaneous multi-physics field analysis on the output port of the overmode waveguide to observe the temperature change caused by the change of the electric field at the output port.The main research work of this paper:1.The theoretical basis of the circular waveguide-rectangular waveguide and hole directional coupler is derived,which provides a theoretical basis for the design of the directional coupler in this paper.2.A circular waveguide-rectangular waveguide directional coupler with a new coupling structure is designed.These coupling structures enable the coupler to have a certain mode selection capability on the basis of power measurement,and provide convenience for the mode analysis in the overmode waveguide,and based on this,the main higher-order modes in the overmolded circular waveguide can be analyzed and identified.3.A method of using multi-physics analysis method to assist the measurement of the mode in the overmode waveguide is proposed.Through thermal analysis,the difference in the electric field distribution of different modes is used to realize the identification of different modes,and the mixed transmission of multi-mode Measurement.The research proves that this method has a good effect for the mode measurement under high power.