Research On Radio Frequency And Terahertz Composite Systems

The terahertz wave is an electromagnetic wave with a frequency between 100 GHz and 10 THz between visible light and microwave millimeter wave.Because of its superior characteristics,it has important academic value and application value in medical imaging,environmental science and satellite communication and so on.In the terahertz communication system,the terahertz mixer is the core component of the receiving front end.Its main function is to realize the spectrum shift between the IF signal and the RF signal in the terahertz band,thereby realizing the functions of up-conversion and downconversion..Firstly,we have established the design and circuit structure of the terahertz mixer.The basic circuit of this subject includes a radio frequency and local oscillator circuit with a height of 50 um etched on a quartz substrate,and an intermediate frequency circuit with a height of 127 um etched on the duroid 5880 substrate.In addition,the WR2.2,WR10,and WR28 rectangular waveguides are the input or output waveguide types used for the RF,LO,and IF ports of the terahertz mixer.Then through the theoretical knowledge and research of each module,the modeling,simulation and optimization of passive circuits are completed.Among them,the electromagnetic simulation software HFSS is used to complete the waveguide-suspended microstrip probe transition,waveguide-microstrip fin line transition,local oscillator low-pass filter,intermediate frequency low-pass filter,RFreduction waveguide and other modules.At the same time,the 3D mode of the Schottky diode used in the mixer is also established in the HFSS,and the parasitic parameters of the diode are obtained through subsequent simulation.Finally,the simulation results of the above passive circuit module are imported into ADS for overall harmonic balance simulation.The simulation results show that the conversion loss(Conversion Loss)of the upconverter and the downconverter is not higher than 14 dB.The measured results show that the total loss of the two terahertz mixers is about 51-53 dB,and the average conversion loss is 25.5-26.5dB,which is consistent with the design specifications.Above all,the work of this topic is summarized and the work content to be carried out in the next stage is given.