Design And Fabrication On Silicon-based Terahertz Waveguide Directional Coupler

As one of the key passive components to realize the directive distribution of power,the directional coupler can be used in the field of microwave,millimeter wave and communication.Compared with the planar transmission line device,the sub-millimeter waveguide type device has the advantages of low loss,higher power processing ability,and easy to interconnection with the measurement system and other solid-state systems,and has become a hot spot at home and abroad.In this paper,a new kind of waveguide coupler is designed,which is compact,ultra wide bandwidth,strong coupling and high directivity,and the process is completed by MEMS technology.Based on summarizing the research and development trends of waveguide and waveguide directional coupler,starting from the design principle of directional coupler,we use multiple coupling holes between the waveguides by putting a waveguide on top of another one to the power distribution.In this paper,a terahertz-coupled waveguide directional coupler with a center frequency of 400 GHz and a bandwidth of 150 GHz is designed by using the electromagnetic simulation software HFSS.The coupling hole has two kinds of “cross” and “triangular”,the simulation results show that the structure has good transmission performance.Taking the connection mode of the test system into account,three topologies corresponding to three kinds of parameters that is the coupling,return loss and isolation are designed.The fabrication of the waveguide directional coupler with high resistance silicon as the structural material is completed based on the deep silicon etching process and bonding technology,and then was metallized by magnetron sputtering and micro-plating.The directional coupler is packaged in a small rectangular unit made of silicon with the size of 6 mm×6 mm×1.36 mm,and is tested by the special matching fixture,then the simulation results are in good agreement with the simulation results.In this paper,the design and fabrication of the terahertz waveguide directional coupler are successfully completed,which breaks the limitation of the traditional style of putting the waveguides in the same plane.The work bandwidth and direction of the directional coupler are improved by using multiple holes,which is of great significance to the research and development of the subsequent terahertz system.