Research On Miniaturization Of Substrate Integrated Waveguide Bandpass Filter

At present,the wireless communication technology vigorously developed by the countries all over the world is mainly focused on the microwave and millimeter wave integrated circuit technology,which can realize the multi-functional hybrid integration of the system,reduce the size and improve the reliability of the system.It has great application value in the fields of satellite communication and personal mobile communication.The filter can be used to filter out specific frequencies in the signal or frequencies outside the band effectively,to obtain or eliminate signals in a particular frequency band.With the continuous development of wireless communication technology,as a significant part of wireless communication system,the filter not only needs to have the advantages of large power capacity,high quality factor and low loss,etc.,but also needs to be developed towards the direction of miniaturization and easy processing.Traditional high frequency transmission structures can't satisfy the requirements of the development of wireless communication technology mentioned above.Therefore a new transmission structure--Substrate Integrated Waveguide(SIW)technology has been proposed in recent years.The substrate integrated waveguide inherits the advantages of the traditional transmission structure and has a wide range of applications in filters,duplexers,couplers and antennas.Of course,the substrate integrated waveguide structure also has some disadvantages,such as the problem of large size at low frequencies.In this paper,the miniaturization and optimization of the SIW band-pass filter are mainly studied.And the paper primarily proceeds from the following aspects:Firstly,the basic theory of substrate integrated waveguide was introduced.From the equivalence principle of the integrated substrate waveguide and the traditional rectangular waveguide,the calculation method of the size of the integrated substrate waveguide is given.The transmission characteristics of substrate integrated waveguide and three kinds of transition structures are briefly described.As well as the basic parameters that need to be calculated and specific implementation processes of designing the integrated waveguide band-pass filter are introduced.Secondly,in the process of filter design,space mapping algorithm and machine learning algorithm are used to design and optimize filters.A fourth-order integrated substrate waveguide band-pass filter is optimized by two optimization methods.Under the premise of ensuring accuracy,the calculation efficiency of ASM and the computational efficiency of machine learning algorithm are both improved lot.In the optimization process,the appropriate optimization algorithm is selected according to the actual situation to ensure the accuracy of the calculation and improve the efficiency of the calculation.Then,a two layer fourth order substrate integrated waveguide band-pass filter based on physical coupling with a center frequency of 24 GHz and a fractional bandwidth of 40% is designed.In order to further improve the performance of the filter,a Complementary Splint Resonant Ring(CSRR)and an Electromagnetic Band Gap(EBG)are introduced into the structure.By changing the size and rotation angle of the complementary Splint resonant ring and the number of electromagnetic band gap,the position of the transmission zeros were changed.The feasibility of the method is proved by simulation.Finally,a dual-mode circular SIW band-pass filter based on mode coupling with a center frequency of 26 GHz and a fractional bandwidth of 25% is designed.In order to improve the performance of the filter,the transmission zero is introduced.By loading two rectangular resonators to introduce two degenerate modes with the same amplitude and opposite phase,the filter produces a transmission zero at resonance.The feasibility of the method is proved by simulation analysis and physical measurement.