Research On Wide-band Circular Waveguide TM₀₁ Mode Actuator

In the application of high power microwave devices,The connection problem between different devices and interfaces is very common.The mode converter is usually used for transition connection when the mode of the required waveforms and the modes of the existing waveforms are different,As one of the mode converters,the output mode purity is higher.A X band compact all waveguide bandwidth mode exciter is proposed and studied in this paper,The input is the standard rectangular waveguide BJ100,The bandwidth of the working group covers 8.2GHz-12.5GHz,the reflection coefficient is less than-25dB,and the output mode clutter suppression system is more than 50dB.In order to meet the requirements of the parameters of the subject,the basic idea of the model excitation is link transformation.The transformation pattern sequence is rectangular waveguideTE^X₁₀-coaxial-circular waveguideTM^d₀₁-Circular waveguide with output aperture,At the same time,in order to meet the needs of the output of different circular waveguide diameter parameters,a caliber transition device is designed.The specific work is as following three aspects:1.The multi section impedance matching theory and the analysis and calculation method of binomial and Chebyshev 1/4 wavelength multiple impedance converter are introduced in detail.It is used for the ladder transition design of rectangular waveguide to shorten the transformation length.2.In order to improve the overall structure stability of the model converter,the excitation mode of the rectangular coaxial transformation structure is analyzed.On the premise of guaranteeing the bandwidth and conversion efficiency,selecting the supermodel coaxial line structure and greatly thickening the diameter of the inner conductor of the coaxial line.It is a great innovation in this paper.3.The distribution characteristics of TM₀₁ field in coaxial TEM and circular waveguide are compared and analyzed,and the efficient transformation of the coaxial TEM to circular waveguide TM₀₁ mode is completed by using the internal conductor probe excitation mode;In order to achieve a larger output aperture connection,a stepped circular waveguide output structure is used.Not only greatly reduces the device length,so that the converter is more compact,but also more effective to suppress the mode output,improve the output purity of TM₀₁ mode largely.4.Made the processing plan,the mode converter is processed in real form,and the related performance test is done by the laboratory near field test platform,and the mode distribution of the mode converter is tested.The vector network analyzer is used to test the insertion loss and reflection characteristics of the converter.The results show that the return loss of the converter is higher than that of 25d B in the full working band of8.2GHz-12.5GHz,and the insertion loss is lower than 0.4d B,and the output purity is higher than 99.5%..