Research On THz Superconducting Receiver Front End

With the rapid development of wireless communication technology,the demand for high-rate,large-capacity communication and ultra-high resolution imaging is increasing,which also promotes the development of wireless communication from microwave to millimeter wave and terahertz.At present,the fifth generation mobile communication technology has covered the millimeter wave band,and the terahertz band will be used in the new generation of 6G communication.Terahertz communication has the advantages of richer spectrum resources,high transmission rate and good direction.Due to the strong atmospheric attenuation characteristics of terahertz waves,polar molecules such as water molecules in the air have a strong attenuation of terahertz waves,so the highly sensitive receiver front end plays a very important role in terahertz communication systems.This thesis takes it as a starting point to study the front end of the terahertz superconducting receiver,and designs a superconducting receiver front end working in the 200-220 GHz band.Firstly,this thesis studies the relevant theoretical knowledge of the front end of the terahertz superconducting receiver and determines the system design scheme.Then,according to the scheme,the design of the core components of the front end of the terahertz superconducting receiver is completed.It includes a horn antenna loaded with a dielectric lens,a 200 to 220 GHz mixer based on a Josephson junction,and a 100 to 110 GHz local oscillator frequency multiplier based on a Schottky diode.In the design process of the horn antenna,the dielectric lens of PTFE material is loaded in the horn to realize the convergence effect of the antenna beam,so as to effectively reduce the sidelobe of the antenna and improve the gain and directivity of the antenna.Through modeling and simulation in HFSS software,the VSWR of the horn antenna loaded with dielectric lens is less than 1.2 in the full frequency band,and the gain is effectively improved to 22.43 dB,and the directivity is significantly improved.In the design process of the local oscillator frequency multiplier and mixer,the passive circuit(CMRC low-pass filter,local oscillator duplexer,RF probe,etc.)is designed with the help of electromagnetic simulation software.The feasibility of the design is verified by harmonic balance simulation,and the physical processing,assembly and test are carried out.When the excitation signal is 5dBm,the maximum output power of the frequency multiplier in the 100-110 GHz band is-23.02 dB.The thesis concludes with the assembly and testing of the THz superconducting receiver front-end.When the fixed IF is 4GHz,the minimum gain of the system is 21.51 dB,when the fixed IF is 6GHz,the minimum gain of the system is 19.08 dB,and the minimum noise figure of the system reaches 8.66 dB in the 200-220 GHz frequency band.