Design Of IF Module For Dual-Port Vector Network Analyzer

With the rapid development of aerospace industry and communication technology,the corresponding hardware facilities need to be innovated rapidly,the characteristics and performance of RF& microwave products need to be tested more quickly,accurately and conveniently.Vector network analyzer is an indispensable instrument for measuring RFµwave products.Based on the basic principle of vector network testing,with the IF receiver as the basic framework and the FPGA chip as the core device of data processing,designing the IF module of the dual-port vector network analyzer.According to different measurement requirements,the input IF signal is digitally processed to obtain the S parameters of the network under test or to perform time domain analysis.Firstly,according to the basic structure and test principle of the vector network analyzer,a fully digital data processing module is designed,which can process multichannel synchronous sampling data according to the test demand variable rate,and transform the signal into the frequency domain by the all-phase FFT algorithm,which suppresses the spectrum leakage caused by data truncation,and improves the accuracy of amplitude and phase detection.In addition,designing a command moudel to realize the test data upload and parse the commands sent by the host computer.According to the actual situation of some RF microwave devices working in pulse signal environment,the S-parameter measurement mode based on pulse-RF excitation is designed in thesis to simulate the actual working environment of some tested networks and measure their performance and characteristics in the working environment.The timedomain analysis mode based on S-parameter is designed to analysis the fault location of cable under different time-domain modes,enriches the function of traditional vector network analysis.Finally,the algorithm and function modules used in the above-mentioned dual-port vector network analyzer IF module are implemented in hardware with a three-channel IF board equipped with FPGA.After digital logic simulation verification,each module and function are tested and analyzed.The test results show that the IF module designed in this thesis can provide different dynamic range by variable processing rate,and can provide more than 105 dB dynamic range without using external gain.Multichannel relative testing can accurately measure the relative amplitude and phase between different channels,and show good measurement stability;S-parameter testing under pulsed-RF excitation can be achieved by precise sampling control and application of specific filters.Time-domain analysis mode can accurately locate cable faults and correctly analyze impedance mismatch types.