Hardware Design And Development Of Portable Vector Network Analyzer

Vector Network Analyzer(VNA)as an electronic instrument can measure signal parameters in the frequency range from a few kilohertz to tens of gigahertz,such as phase and amplitude of signals in the circuit.In addition,VNA can also measure complex networks such as ladder networks or hybrid networks.Currently,there are some drawbacks to VNAS on the market,such as bulky size,easy damage,high cost and price,especially for large instruments.In addition,its use process is relatively complex and requires certain professional knowledge,otherwise it will affect the accuracy of the measurement results.The maintenance and maintenance costs of VNA are relatively high in the later period,and users need to perform regular maintenance to ensure the normal use of the instrument.The purpose of this paper is to design and develop a portable VNA to address the problems of traditional VNA in response to the shortcomings of the above devices.The device can measure the Sparameters of the device under test within the frequency range from 100 k Hz to 6 GHz,with reasonable price,light weight,high measurement accuracy and wide application range.The main research contents and achievements of this paper are as follows:Firstly,the basic concepts and principles of microwave RF circuits were introduced from the theoretical level,the basic structure of VNA was introduced,the various components and various types of errors existing in the internal were combed,and the principle of error calibration was introduced,among which the TRL algorithm calibration was introduced in detail.Based on these basic knowledge,the starting point of the research and design of this paper was introduced,and the internal structure and various component schemes of the portable VNA were studied from the overall level,among which the RF source circuit,signal separation circuit and receiver circuit were introduced in detail.Secondly,according to the basic structure of the portable VNA,the hardware design of the portable VNA was designed in a modular way from the hardware level,selecting appropriate chips to construct circuit modules,including system power modules,radio frequency source modules,local oscillator modules,attenuation gain modules,signal separation modules,receiving frequency changing modules and ADC signal sampling modules.Among them,the radio frequency source module adopts the frequency synthesis sweeping frequency method to generate,and the receiver adopts the two-stage differential frequency changing method to ensure more accurate sampling of the intermediate frequency signal for the subsequent ADC module.Then,according to the circuit modules,Cadence software was used to draw the hardware schematic diagrams of each module and analyze the working details of each module.Based on the parameters of each circuit chip,different simulation software were used to simulate some circuits in order to make them meet the expected results.Finally,according to the circuit schematic,the PCB board was produced and made into a physical object.Through various tests on the physical system under the same conditions,the test results verified that the test system designed in this project can measure S-parameters more accurately,and the measured parameter indicators meet the design requirements of this paper.The measurement accuracy is comparable to that of other instruments on the market,and the measurement accuracy effect is better,which has practical engineering significance.In addition,the system designed in this project is compact and lightweight,with the characteristic of portability.Based on the research objectives and research results of this paper,the designed hardware test system in this project meets the design requirements.Therefore,the product designed in this project can have certain practical value.