The Development Of Terahertz Band Noise Source

With the gradually deepening research on terahertz waves,the advantages of terahertz waves in communication,imaging,guidance and other fields are emerging,so mastering terahertz technology has great national defense significance and livelihood value.The noise will affect the signal quality to constrain the relevant performance of the system,so the measurement of the noise coefficient of the device or system and the quantitative as-sessment of its noise index have a very strong practical significance.At present,the noise coefficients of devices or systems relating to the terahertz band are mainly measured using blackbodies,but blackbodies are usually bulky and inconvenient in measuring,and their prices are also very expensive.In this paper,based on the variable-temperature noise source method,a variable-temperature noise source operating at 195GHz-205GHz is de-veloped,which can accurately change temperature and control temperature in the temper-ature range of 20K-260K,and a noise coefficient measurement device is built to complete the accurate measurement of small noise devices in this frequency band.The main work is as follows.1.Determination of noise measurement methods.Briefly described the two com-monly used noise measurement methods - Y-factor method and gain method,from the basic principle of the Y-factor method combined with the graphical form of the traditional cold and hot load method to improve the measurement of more accurate variable tem-perature noise source method.Because compared with the traditional hot and cold load method of two groups of data,it gets more data sets,and the results obtained after linear fitting will be more accurate.At the same time,the wireless variable temperature noise source scheme used in this paper does not need to consider the influence of temperature gradient distribution in wired transmission,but only the attenuation of wireless transmis-sion and the loss of wired transmission line,and the uncertainty will be smaller.Based on the overall structure of the test device of the variable-temperature noise source method,the calibration equation is studied,and the equivalent noise temperature is accurately cal-ibrated to the output of the variable-temperature noise source.2.Research and design of the components related to the variable temperature noise source.The research and design of the variable temperature load,transceiver antenna and sealing window were carried out.Based on the excellent simulation results,the corre-sponding drawings were made with the help of Solidworks and Auto CAD software and the processing of the casting board was carried out.3.Design of terahertz module.The design of the low-noise amplifier was carried out,including the selection of the chip,stability analysis,the design of the waveguide microstrip transition structure,and the design of the amplifier chip chamber.After pro-cessing and assembly,the relevant measurement link was built and the two-stage cascade amplifier was tested,and the final test results met the design specifications.A bandpass filter was designed considering the need to suppress spurious waves when testing the am-plifier gain,and it was also used as the measured part for relevant tests.4.Test system construction and testing.After the design of the relevant devices is completed,the noise coefficient measurement is required.The test plan was established,the test platform was built,and the filter under test was tested according to the test proce-dure,and the results of this test were compared with those of the vector network analyzer.Subsequently,the measurement uncertainty analysis of the test system was performed,and the source of uncertainty was mainly related to the mismatch between the interfaces.