Research And Implementation Of Vector Network Analyzer Based On Impedance And Transmission Characteristics

In the field of modern microwave radio frequency,Vector network analyzer which is a common instrument for testing S parameters of radio frequency network,.Because of its high price,huge size and heavy weight,the vector network analyzer can only be used in certain places.Aiming at these existing shortcomings of vector network analyzers.We design a portable vector network analyzer that has the fair price,small size,wide using palces and test accuracy which can meet normal testing.The main content of our research is to design a dual-port portable vector network analyzer which can measure the S parameter of the device under test or the network under test in the range of 50KHz-4GHz.This dual-port portable vector network analyzer can set the test frequency band and testing parameter through the display screen,then it can display different measurement characteristics at the same time,such as the amplitude-frequency characteristics and phase-frequency characteristics of S-parameters,etc.The main research work of this paper includes the following aspects:This research introduces the basic principles and basic structure of vector network analyzers at first,and conducts theoretical analysis on key circuits like signal separation circuits.We also introduced the error correction principle of the vector network analyzer,as well as the reason and type of error.The focus of the introduction which is the SOLT calibration algorithm and mathematical theory formula used in this system.The study also gives a detailed description of the method of measuring S-parameters.After that,we describe the indicators and design schemes of the system.The research carried out theoretical design and device selection for several main circuits of the system,including signal separation circuit,radio frequency signal source circuit,intermediate frequency processing circuit,power supply circuit.The circuit model used by the system that is obtained by comparing each scheme.Then introduce the error model which is using in system.This thesis carry on the simulation and circuit design to each circuit module.First,design for the signal separation circuit which is using bridge,the RF signal circuit,the medium frequency circuit and the power circuit.And then design a new signal separation circuit which is using the directional coupler,and RF signal circuit which is for upgrading the vector network analyzer.Finally,the system is simulated and analyzed,and the system is tested and verified by several DUTs and circuits under test.Finally,we perform a single tone test on the frequency and ppm of the system output signal.By comparing with the spectrum analyzer,the accuracy of the output signal is verified.We test the same circuit by comparing it with the Agilent E5071C vector network analyzer in the same frequency band,and then get several sets of different test curves.By comparing the test results,it shows the vector network analyzer designed in this research can correctly test the S parameters of the tested network;and it has some advantages like lower price and small size and etc.It has a good practical value.