| Terahertz wave is located between microwave and infrared bands in electromagnetic spectrum.It has many unique advantages such as high resolution,high penetration and low energy,which makes terahertz technology have great application value in various fields.Directional couplers,as the core passive components for power directional synthesis and distribution,play an important role in modern electronic systems.It has become the main research trend in the field of microwave and radio frequency to achieve excellent performance and miniaturization of volume.Compared to planar transmission structures,rectangular waveguides have the advantages of low loss and high transmission performance,and are easy to connect with test systems.In order to realize the broadband and good directivity of the coupler,the waveguide directional coupler with the center frequency of 380 GHz is designed and analyzed.The main work is as follows:1.Based on the research and summary of the development status of THz directional couplers at home and abroad,and combined with the theory of rectangular waveguide field and the basic design theory of couplers,two new types of rectangular waveguide couplers with a central frequency of 380 GHz are designed,one is a branch-line coupled Tian-shaped coupler and the other is a small-hole coupled pentagonal coupler.The effects of structural parameters on the performance of the couplers are studied and analyzed.Finally,the optimal sizes of the two couplers are obtained.The 3dB Tian-shaped branch waveguide directional coupler with simple structure and easy processing is mainly studied.The simulation results show that the coupler has better directionality than 20 dB in the operating frequency range of 70 GHz,and the average insertion loss is less than 0.1dB,which realizes the working frequency bandwidth,good directionality,strong coupling and low loss.The pentagonal porous coupler has a working frequency range of up to 160 GHz and a directionality better than 25 dB,but But the processing of coupling holes is more difficult.2.The Tian-shaped branch-line directional couplers are fabricated by a mature micro-machining technology.In order to facilitate the test,three different coupler topologies were designed.The corresponding masks were fabricated by AutoCAD software,and the Tian-shaped couplers were prepared by bulk silicon MEMS process and UV-LIGA technology respectively.The MEMS process is expensive and limited by silicon materials,while the UV-LIGA technology reduces the processing cost and the process is simple.Therefore,the complete coupler is processed mainly by UV-LIGA technology.The technology takes negative glue as the main material,develops more mature and can achieve larger aspect ratio.Finally,a test platform is set up to test the electromagnetic performance of the coupler.The test curve and the simulation curve trend are basically the same,but the actual value of the coupling degree is about 1.6dB larger than the simulation value,and the measured value of the return loss is about 6dB smaller than the simulation value,and the cause of the error is analyzed.In this paper,the 380 GHz waveguide directional coupler is studied,and the modeling and simulation of the waveguide coupler is successfully completed.It has certain reference value for the research of terahertz coupler. |
PDF Full Text Request