Realization Of Virtual Frequency Spectrum Analyzing Instrument Based On USB

The virtual instrument concept was proposed in the mid of 1980s. With more than 20 years development, it is used widely instead of some traditional instruments in more and more fields, such as teaching experiment, electronic measurement, analysis test, industrial control and so on. The topic of this dissertation originates from the project of Xi'an Science and Technology Committee, which is for the research of virtual system base on USB. The goal of this paper is to accomplish virtual frequency spectrum analyzing instrument base on USB of high performance and low price.The paper adopts USB2.0 interface chip CY7C68013 as the core of the design of system instead of other bus interfaces with bottleneck problems in real-time transmission and realizes real-time large bulk data transmission between the host and the device, without outside memory. In addition, the paper uses QUARTUSII software to simulate the data collection, date transmission and frequency measurement circuit of double channels' signal at one time and realizes the synchronous collection, transmission and frequency measurement of double channels' signal. Moreover, the special device driver and the loader driver are developed in the WIN2000 environment and the application program is developed with LabWindows/CVI software by ourselves, whose interface is like the panel of traditional instrument, but more flexible and more functional than it. The application program combines the functions of all kinds of signal-analysis and signal-processing. On the basis of the above work and the current situation of the domestic and international medical instrument, the paper proposes the idea of applying the instrument to the analysis and process of bio-electric signal. The paper takes the heart electrical signal as the researching object and accomplishes the time domain and frequency domain analysis related to it with the instrument.The effective sample speed of this instrument is 1MHz, the resolution is 12bit. It can do real-time data collection of double channels' signal incessantly for a long time and all kinds of the time domain and frequency domain analysis. So, the instrument can be used wildly in many fields, such as medical signal processing, signal collection and analysis, craft process control and so on.