Extra Wide Stopband Waveguide Low Pass Filter Design

With the rapid development of science and technology,the application of satellite communication is becoming more and more extensive,and it is developing in the direction of broadband and multiple frequency bands.Microwave filter is an extremely important component in satellite communication system.In the field of satellite communication,microwave filter requires wide stopband,low insertion loss,high power capacity,high frequency selectivity and miniaturization.Rectangular waveguide filters are widely used in satellite communications because of their high power capacity and low insertion loss.However,due to the characteristics of multimode transmission in rectangular waveguides,the out-of-band suppression characteristics of traditional waveguide low-pass filters are not ideal,which limits their application capabilities in broadband applications.This article mainly focuses on the suppression design of the extremely wide stop-band characteristics of waveguide low-pass filters.Technology development theory and experimental research.The design method of ultra-wide stopband waveguide low-pass filter proposed in the paper mainly realizes the staggered distribution of out-of-band resonance through the local simulation and optimization of the inductance unit circuit,which can complete the filter design relatively quickly.The traditional design completely relies on the idea of global parameter optimization and requires a lot of simulation computing resources.First,the design theory of microwave filter is systematically analyzed,and the design idea of the filter is summarized.The research status of waveguide low pass filter is introduced in detail,and the relevant theoretical knowledge for designing wide stopband filter is analyzed emphatically.Secondly,the method of combining field and circuit is used to design the wide-stopband waveguide low-pass filter,which realizes the rapid and accurate design of the waveguide filter.Based on the guided wave field theory and combined with threedimensional electromagnetic simulation analysis,a high-order harmonic suppression scheme for the filter inductor unit circuit is proposed,that is,by changing the height and length of the waveguide section of the inductor unit,the out-of-band resonance frequency of each waveguide inductance element is realized.The points are staggered to achieve the purpose of wide stop band suppression design.Finally,the asymmetric inductance unit structure is used to further flexibly control the out-of-band resonance frequency of each inductance unit in the filter,and finally realize the design of ultra-wide stop-band waveguide low-pass filter.Simulation and experimental tests show that the passband of the X-band waveguide low-pass filter is9.7GHz?11GHz,and the 45 d B stopband rejection is in the frequency range of11.8GHz?45GHz,which reaches 6.43 times the working bandwidth of the main mode of the BJ120 waveguide(9.84GHz?15GHz).