Research On Multimode Antennas Based On Substrate Integrated Waveguide

With the rapid development and upgrading of communication system,the research based on the technology of substrate integrated waveguide?SIW?has become a hot spot in microwave and millimeter wave antenna field.In particular,the fifth generation mobile communication system?5G?has begun to be deployed,and the research and application pay more attention to millimeter wave,the characteristics of high loss in millimeter wave band make the traditional microstrip patch antenna unable to meet the needs of the corresponding antenna design;and the disadvantages of metal waveguide are also obvious with large volume,high price and inconvenient processing.The technology of SIW combines the microstrip's advantages of low profile,low cost,easy to integrate with planar circuit,and also has characteristics of low loss and high power capacity,so it has a good research value and development.The purpose of our research is to use the cavity mode theory to analyze the SIW cavity,and reasonably stimulate the modes in it,thus,the performance of the antennas can be improved in various aspects.The main contents of the thesis are as follows:1.The electric field energy distribution of a high-order mode is reasonably used to form a four-slot array antenna,thus the gain of a single antenna unit is improved.Compared with the traditional four-slot array based on TE₂₁₀mode,the proposed array antenna does not need an additional feed network,so the feed loss is reduced,the antenna gain is improved,what is more,the processing and manufacturing of the antenna are easier.2.Two multimode broadband antennas are designed separately.The first one combines four modes,achieves a relative bandwidth of 16.4%and a maximum gain of 9 dBi.The second one reasonably excites three modes,obtains a relative bandwidth of 19.1%and a maximum gain of 9.67 dBi.In addition,the differential feed structure is introduced to the second antenna to improve its performance,the result shows that the radiating direction of the patterns are corrected,the bandwidth and gain of the antenna are added to 22.2%and 11.26dBi,respectively.The folded SIW structure is also added to the antenna,and the sidelobe of the pattern reduce at most 14 dB,besides,a gain zero is introduced by the couple of the modes,which is benefit to the filter performance.3.A multiband antenna with four bands is firstly designed,the proposed antenna excites two pairs of orthogonal modes with linear polarization,besides,the resonant frequencies of each mode can be independently adjusted,making it applicable to the multiband antenna field.What is more,the two excited cavity modes and two patch modes can be separately combined,to generate circularly polarized radiation,forming a dual frequency circularly polarized antenna.