Design Of Vector Network Analyzer Testing System And Implementation Of Some Key Circuit

Since entering the 21 st century, informatization, digitization, network and intelligence have become significant signs in the human world. The space is filled with microwave RF signals, which leads to the rapid development of information industry. As the basis of information, data system and terminal, microwave RF devices and components are in the explosive development stage. Testing is the foundation of the development of science and technology. As one of the most important testing and evaluation tools of microwave RF components, vector network analyzer has to deal with all kinds of new demands and meet instrument functions, economy and practicality in different cases.This paper aims to design an economical network analyzer with innovative architecture, which can meet the demands of microwave RF circuit components research and production testing in industries such as communication system and information terminal. It achieves the testing capabilities of basic network parameters, has very high performance-to-price ratio and can be promoted in large scale.This paper mainly consists of the following aspects:(1) Making full use of the semiconductor industry technology progress and achievements and using integrated circuits of AD9361 as transceiver core with multi-channel and high performance to design the system. Simplifying the receiver from traditional three channels or four channels to two channels can not only reduces the equipment cost, but also avoids the mutual interference between channels.(2) Designing a new type of directional coupler with the capacitance compensation and multiple-class cascade microstrip line. Traditional single section microstrip directional coupler is difficult to achieve the target of wide frequency range and high directivity. However, utilization of capacitance compensation and multiple-class cascade can significantly optimize the performance of the directional coupler and make up for the inadequacy of frequency range and directivity.(3)A module of reverse signal isolation is designed, which uses the characteristics of the amplifier that the signal is amplified in forward direction and isolated reversely. Using a way of two levels of low noise amplifiers with fixed attenuator can not only reduce the interference from reflected signal to the reference channel, but also compensate the loss produced by modules such as power splitters ordirectional coupler before the signal arrive the device under test.(4) Adding a conversion circuit to upraise the low frequency to 90 MHz because that the AD9361 can not cover frequency range from 300 KHz to 70 MHz.(5) This paper also adds a preamplifier and controlled attenuator before AD9361 to improve the sensitivity and dynamic range of the receiver.Paper embarks from the function and index of the system and analyse the index demand of each unit. During the entire system design process, I have given full consideration to a variety of issues in advance to design and simulate each unit module. Comparing the testing results of this paper with the results tested by standard vector network, the expected goals have been reached.