Analysis Of Impedance Characteristic Error Of Vector Network Analyzer

Vector network analyzer has been decades of development history,operating from a few kHz to hundreds of GHz frequency band,and they are widely used in microwave field most of the characteristic impedance of 50?.With the development of microwave technology continuously,the network to be measured often deviate from 50?,some commonly used microwave devices of input and output impedance are only a few ohms,and some of the high impedance devices of input and output impedance can be as high as hundreds of ohm,even thousands of Europe.50? characteristic impedance of the vector network analyzer is used to measure the measured network of 50? will bring test error,in order to carries on the analysis and experimental verification,this paper made the following work:This paper introduces the concept of S parameter of microwave network,introduces the basic testing principle and basic structure of vector network analyzer,and introduces the function and principle of each structure in detail.Secondly,the error correction principle,error types and causes,different calibration methods and their calibration accuracy are introduced.The error model and error correction formula of single port,the error model of double port and its error correction formula are mainly introduced.Then introduced in this paper,the experiment scheme,the first is through the coaxial transmission line impedance calculation formula of air line impedance calculation formula is deduced,and then design the standard impedance measured parts,precision machining made twelve different impedance of 2.4 mm coaxial air line inner conductor and two 2.4 mm outer conductor,the last theory to calculate the single port reflection coefficient,dual port reflection coefficient and transmission coefficient.Finally,time-domain and frequency-domain measurements are made respectively.In the time-domain state,the impedance corresponding to each position along the air line can be clearly seen.The test results are close to the theoretical values.In the state of frequency domain,the test data obtained by single port and double port measurement are compared with the theoretical calculation.Single port error analysis result has the following three conclusions:one is the near 50? characteristic impedance measurement error is relatively small,deviatingfrom the 50? characteristic impedance,the measurement error has a tendency to increase.The measurement error of air line with different characteristic impedance increases with the increase of frequency.Three is the error of measurement is more sensitive to end termination load characteristic,termination 50? load measurement error is relatively small,and the termination open circuit and short circuit,the measurement error is relatively large.The double port error analysis results have the following two conclusions: 1.The measurement error of air line with different characteristic impedance increases with the increase of frequency;2.Second,near 50? characteristic impedance measurement error is relatively small,deviating from the 50? characteristic impedance,measurement error has a tendency to increase.