Research On Detection System Of Weak Signal Based On Virtual Instrument Technology

With the development of science, more and more problems of weak signal detection appear in each field and it is urgent for the detection. Weak signal which means small amplitude and signal that is submersed in noises, is not easy to be detected .Weak signal detection is a new developing science that employing neoteric electronics and signal processing technologies to get useful signal from noises and is significant to study on.In this paper, theories of the weak signal detection in common use are briefly analyzed. Then, digital averaging is studied in detail. As to the shortage of digital averaging theory , an sampling processing arithmetic is presented which don't need the support of external trigger source. After this, system based on VI technique is designed. The main content of this paper goes as follows:Firstly, advantages and disadvantages of the theories in common use are compared, digital averaging is studied and then, the case of same sequence samples to have same phases without external trigger source is used to simulate the case when there is an external trigger source to make the same sequence samples the same phases and the simulation is done.Secondly, as to the shortage of digital averaging theory, an algorithm is presented. The new algorithm does not need support of an external trigger source. It acquires the same samples per period by sampling processing algorithm and then, samples of a same phase can be added as the way of sampling digital averaging theory does. The error of this algorithm is analyzed and simulation shows that this new algorithm works effectively.Thirdly, a weak signal detection system is designed based on the new algorithm. Low noise amplifiers such as AD8221 and OP27 are used in signal conditioning circuit that is to amplify, filter and isolate the weak signal. This circuit is designed to adjust gain optionally and reject common mode interference and filter out 50 Herz power frequency interference.Finally, software for the system is implemented,which includes data collecting program and the algorithm program. And an experiment is made to test the system.