Research On Millimeter Wave Circuit Based On Gap Waveguide

With the rapid development and commercialization of mobile communication in recent years,the low-frequency spectrum resources are occupied by various communication systems,thus the spectrum resources are becoming increasingly tense.The research of high-frequency band has been paid more and more attention by researchers.At the same time,the popularization of the theory of internet of everything makes the explosive growth of communication mobile data,and the requirements for the quality and speed of microwave and millimeter wave communication technology are higher and higher.For the devices in these communication systems,their highfrequency performance has attracted more and more attention of researchers,experts and scholars.As a new type of transmission line,gap waveguide uses the periodic arrangement of Electronic Band Gap unit structure to introduce the band gap to make the electromagnetic wave only propagate in a specific direction.In order to limit the dissipation of electromagnetic wave in the vertical direction,it is introduced into the upper and lower reflection layers,and with air as the transmission medium,it greatly reduces unnecessary loss and can be processed by printed circuit board process,It provides a new research idea to solve the problems of large loss of traditional microstrip line and difficult processing of rectangular waveguide in millimeter wave band.Based on this,this paper focuses on the application of gap waveguide technology in microwave and millimeter wave passive devices.Firstly,based on the introduction of the classification of gap waveguide,the analysis of the basic principle of ridge gap waveguide and the design of parallel plate cut-off bandwidth,a broadband bandpass filter based on ridge gap waveguide is proposed.The gap waveguide structure replaces the original air gap with a layer of dielectric plate,which makes the gap height more stable and more convenient to convert with microstrip line,The filter designed with this kind of gap waveguide adopts the cascade mode of U-shaped resonator and L-shaped resonator,which reduces the repeatability of the structure and increases the bandwidth of the filter.The simulation results show that the filter can achieve 16.7% relative bandwidth,with return loss less than-15 d B and insertion loss less than 0.8d B.It has the advantages of wide bandwidth and low loss.Then,based on the mushroom-like EBG structure and the ridge gap waveguide technology mentioned above,a single band 3d B directional coupler is proposed,and then the surface current of the patch is changed by loading branches to realize a dual band 3d B directional coupler.In addition,a 90 ° corner is proposed to feed it conveniently.The simulation results show that the dual band coupler can realize two passbands at 21 GHz and 35 GHz,with the insertion loss from input to through end and coupling end is basically less than 3.8d B,the return loss is less than-15 d B,the isolation is greater than 20 d B,and great phase balance is achieved.Finally,a loaded branch line resonator with dual-mode response is designed based on the ridge gap waveguide technology,and a dual frequency band-pass filter with three transmission zeros is proposed.The second passband is controlled by the resonator loaded branch line,which widens the bandwidth.Through simulation and experimental verification,the filter forms two passbands at0.7-21.3GHz and 27.3-28.6GHz respectively.The insertion loss in the two passbands is about 1d B,the return loss is less than 15 d B,and there are three transmission zeros.It has the characteristics of low loss,good frequency selectivity and strong suppression suppression outside the passband.In addition,the gap waveguide technology makes the filter self encapsulated and easy to process.