Design Of Terahertz Broadband Harmonic Mixers Based On Schottky Diode

After the exploration and development in recent years,terahertz technology has been gradually applied in communication,security inspection,radar detection and other fields.In the research and development,production,debugging and maintenance of terahertz system,it is necessary to use corresponding frequency measurement instruments to provide accurate data support.As an essential part of the measuring instrument,mixer is located in the front end of the test system receiver,and its performance will directly affect the whole test system.In this paper,the application of Ethernet Hertz measurement instrument as the background,carried out the study of the terahertz broadband harmonic mixer.First of all,summarize the commonly used transmission lines in the terahertz band,understand the characteristics of schottky diode and the working principle of even harmonic mixer,and on this basis to achieve the establishment of the accurate model of the diode in the terahertz band,that is,to build a 3D electromagnetic model of the diode.Secondly,after mastering the mixer design process,based on the working principle of Schottky diode,different terahertz transmission lines and Schottky diode chips are used respectively.The probe structure,filter structure and duplex structure are designed by HFSS software,and the harmonic balance simulation of the whole circuit is carried out by ADS software.Finally,the design work of 140GHz-220 GHz sub-harmonic mixer and120GHz-220 GHz fourth-harmonic mixer is completed,and the performance of these two mixers is tested and verified.It can be seen from test result of mixers,the operating bandwidth of the 140GHz-220 GHz subharmonic mixer can cover the full WR-5 waveguide band,and its test conversion loss results are 9-14 d B.And in the band of 143GHz-220 GHz,the conversion loss of the mixer is 9-12 d B;The operating bandwidth of the 120GHz-220 GHz fourth harmonic mixer exceeds the recommended band of the WR-5 standard waveguide,with a relative bandwidth of 58.8%.The loss of the mixer is 12-18 d B at the full RF frequency,and is 12-15 d B in the band of 140GHz-180 GHz.Both mixers achieve good conversion loss and significantly increase the operating bandwidth of the mixer.It is expected to be applied in the corresponding frequency band of terahertz measuring instrument to improve the working bandwidth of them,which is of great significance to the application of terahertz technology.