Design Of Portable Vector Network Analyzer Based On AD936X

Vector network analyzers is a widely used instrument in the field of microwave measurement,which can be regarded as multimeter for the design of microwave electronic circuit components.However,traditional vector network analyzers have a series of problems,such as large size,heavy weight,high price,and poor versatility.They not only cannot adapt to complex and changing off-site testing environments but are also difficult to use in large quantities in teaching experiments,factory testing,and other fields.The research goal of this project is to design a portable vector network analyzer based on AD936 X to solve these problems of traditional vector network analyzers.Based on the research goal of this project,the work of this paper is mainly divided into the following four parts:(1)This paper investigates the error calibration model of vector network analyzer from a theoretical perspective,and outlines relevant calibration methods.Based on this,an architecture was established for the design of a portable vector network analyzer by referring to the structural characteristics of traditional vector network analyzer systems.The architecture includes the host software,the system’s core transceiver board,and the signal separation circuit.Design specifications were provided accordingly.(2)This paper has completed the hardware selection and design of the entire system based on the implementation plan of the system architecture.The system core transceiver board adopts the scheme of ZYNQ7035 and AD9361 chip.ZYNQ7035 integrates the microprocessor with FPGA,and AD9361 contains all the circuits of the RF transceiver frontend,greatly improving the system integration,reducing the system volume and power consumption.The signal separation circuit adopts the design of dual directional couplers and four RF switches to meet the measurement requirements of the portable vector network analyzer with dual ports.(3)This paper has completed the software design of the entire system according to the system architecture and hardware structure.The software design includes three parts: the engineering design of the programmable logic end in the ZYNQ7035,the bare-metal engineering design of the microprocessor end,and the host software design.The engineering design of the programmable logic end is responsible for implementing the dynamic configuration of the AD9361 and the complex frequency domain processing of digital signal,while the bare-metal engineering design of the microprocessor end is responsible for the data transmission between the programmable logic end and the host software.The host software is responsible for the calibration algorithm processing of S-parameters and measurement display.(4)This paper has completed the system testing and validation of the portable vector network analyzer.The correctness of the system hardware and software design is proved through testing the system output spectrum and the bare-metal engineering design of the microprocessor end.Through error and calibration analysis of the system,a comparison of measurement results of S-parameters and other microwave engineering parameters between this system and standard instruments is achieved,proving the accuracy of S-parameters and other microwave engineering parameters measurement,and realizing the design goals of miniaturization,portability,low cost,and good versatility of the vector network analyzer.