Research On IF Characteristics Of Terahertz Superconducting Tunnel Junction Mixer

Terahertz(THz)technologies have broad prospects in both fundamental and applied sciences,and it is an important band for astronomy and atmospheric research.In a modern high-sensitive THz system,one of the key modules is low temperature superconducting mixers.A promising one among them is Superconductor-Insulator-Superconductor(SIS)mixers,which have reached sensitivity close to the quantum limit.High sensitivity superconducting SIS receivers are playing an increasingly important role in the research of the radio astronomy.Superconducting RF receiver front-end system is the key part of it is in the forefront of numerous subsystems,the stand or fall of its performance to the back-end signal processing and the receiver has a vital influence the overall noise performance,so the pursuit of the front-end system is necessary for the performance of the constituent components.In low temperature environment,the connection in the mixer,the Bias-T and low temperature and low noise amplifier between the coaxial cable directly affects the performance of the superconducting mixer,making the design at the same time has good thermal isolation and electrical properties of coaxial cable is particularly important.Bias-T is for the active(low temperature and low noise amplifier,superconducting SIS mixer),through radio frequency(RF)channel to provide dc voltage,and effectively restrain RF signal leak of a device.Its role is mainly to provide dc bias and intermediate frequency output pathway,require a good signal isolation between the two.Low noise amplifier working environment temperature is 4k,working within the refrigeration Dewar,so we must to offer low noise amplifier offset bias,a study on low temperature characteristic Bias-T.Based on the above background,this paper has carried out for ascension of the practical need of terahertz superconductive detector sensitivity,completed from the experiment of THZ receiver front-end coaxial cable and low temperature characteristics of terahertz dc bias source characterization.This thesis mainly working content and results are as follows:1)Analyzed the three-channel and hardware structure of the characteristics of the vector network analyzer,based on 12 error model and eight error model,respectively,the SOLT calibration method is introduced and the TRL calibration method.This paper analyzes the hardware topology of the two methods,and makes clear formulas for the two calibration methods;2)Using the TRL calibration method,the thru-line method was used to test the properties of the coaxial cables of different materials at ambient temperature and low temperature.At low temperature,the loss of cable loses significantly,and the propagation constant is largely unchanged.The cable that compares the same material can be found,the loss of the cable is mainly introduced by conductor loss;3)Based on the measurement of thru-line,the scheme of SOLT calibration under low temperature was proposed,and the characteristics of the system under normal temperature and low temperature were tested.The coaxial switch characteristics of temperature and low temperature were measured,and the temperature and low temperature characteristics of the two types of pt-t were measured successfully.The results showed that the insertion loss of the low-temperature Bias was reduced,and the low temperature characteristic was in accordance with the application of astronomy.Finished on paper from the theoretical calculation and experimental measurement of terahertz superconducting tunnel junction detectors intermediate frequency characteristics of research,for the spatial development of terahertz detectors provides the basis for effective and reliable reference for the design.