Virtual Instrument Technology Research

Virtual Instrument(VI) is a new concept which has been advanced by American National Instrument (NI) corporation firstly in the middle of eighth decade. The system of virtual instrument is a great breakthrough to traditional instrument, and which is the production of combination of computer and instrument system technology. In the system of VI, the computer's outer devices is usually used to provide a platform to the input & output of signal, computer is used to solve the problem of the signal real-time disposal and analysis, which is the key point of the whole instrument. The advancement of the concept of Virtual Instrument brings the test technology into a new developing time.VI and basic system character test technology is regarded as the task's directional idea. The paper introduces the theory of a kind of four-port linear network frequency characteristic test equipment based on VI technology carefully. On the ground of these theories, it analyses the foundation of theory of choosing the key module and the way of design, and discusses the key technology of this platform including swept signal source based on DDS and PLL technology , the signal adjustment part composed of AGC and ellipse filter and high speed data acquisition system based on PCI local bus. In the process of design, mainly I have finished the following work: (1)investigated the development status of VI and made sure it's design way;(2)the design of the swept-frequency signal source;(3)the design of signal adjustment modle;(4)finished the design of high-speed data acquisition card; (5) dubuged the whole instrument and performance analyse. The equipment mainly is applied to the measurement and analysis to filter, wide-band amplifier, frequency detector and the other active or passive linear network frequency characteristics .