Detection Of Weak Signal Based On Digital Correlation

The aircraft icing is regarded as one of the six meteorological factors that affect the flight, and is a very big danger to flight safety, so aircraft icing sensor has an important role on ensuring the flight safety of aircrafts. The fiber-optic icing sensor provides a new method to resolve it. In consideration of the background light and electronic thermo noise, this thesis proposes digital correlation to detect the weak signal. This method can detect the signal that can't be detected in traditional opinion. So the precision of weak signal detected is enhanced much.This thesis introduces the causation and statistical characteristics of noise. In the base of the research into the digital correlator and the characteristics of the fiber-optic icing sensor. This thesis designed the overall scheme, the digital correlation method and emulated the correlation method with LabWindows8.0. The emulation proved the algorithm available. A data acquisition board based on TMS320LF2407A was made, and the corresponding software was designed. A series of experiments were carried by use of square signal, sine signal and sine signal stacked with second-harmonic and third-harmonic from signal generator. These experiments verified that the measurement for cycle signals stacked with strong noise worked well. At last, a series of experiments were carried with the signal from the real fiber-optic icing sensor. The test results accord with the results from the analog correlator.A series of experiments indicates that the digital correlator can measure the amplitude of cycle signals stacked with strong noise accurately. Digital correlator is superior to analog correlator in dynamic characteristics, linear distortion, zero drift and so on. So digital correlator has a good prospect for its wide application in industry, such as weak-light, small displacement, tiny vibration, micro temperature difference, micro electric capacitance, weak magnetic, weak conductance, feeble current and so on.