Research On Weak Photo-electric Signal Detection And Acquisition Technology

Up to now, the weak photo-electric signal detection technology has attracted more and more attention in many fields, what's more important is the fact that it is an edge-cutting subject in Aeronautics and Astronautics. With the development of science and technology, the precision of weak photo-electric signal detection system is required to be higher. Weak signal detector with better accuracy is the urgent task in many fields. So the research on weak photo-electric signal detection and acquisition is significant in practice.Firstly, according to the pA level weak photocurrent signal to be detected in the research, the noise in the detection system and its impacts on the system are analyzed. The front adjusting circuit based on components of low noise and high precision is designed. The magnification of two order amplifier circuit is 107, and the cut-off frequency of the anti aliasing filter circuit is 7.8kHz. According to the characteristics of the signals to be tested, the parameters of components of amplifying circuit and filter circuit are calculated. The Multisum software is used to simulate and verify the circuit. And then the hardware circuit is designed after the simulation and verification.Secondly, to complete analog to digital converter(AD), the output signals of the front circuit are input to the 24 bit AD conversion circuit. And the digital signals, which are converted by AD conversion, are transferred to digital signal processing(DSP) to detect the amplitude and frequency. For the amplitude detection of the weak photocurrent signals, the reverse gain compensation method is used, the Duffing oscillator is improved, which increased the amplification gain, so the amplification gain can be regulated to observe the change of the phase trajectory, then the amplitude of the signals can be calculated according to the chaos threshold and the amplification gain. For the frequency detection of the weak photocurrent signals, the zero crossing method is applied by using the intermittent chaotic phenomenon of the Duffing oscillator. The intermittent chaotic phenomenon of Duffing oscillator is judged by whether the speed orderly crosses the zero. And then the frequency of the measured signal can be indirectly calculated by calculating the cycle of the intermittent chaotic phenomenon.Finally, the Matlab simulation of the Duffing oscillator to detect the amplitude and frequency of the signals is conducted, and the amplifier circuit, the filter circuit, AD convertion circuit and DSP control circuit are connected and debugged. A standard test signal is generated by partial pressure method, which is formed by large resistance, to detect the amplitude and frequency, the measurement error of the amplitude detection is ±0.26%, the measurement error of the frequency detection is ±0.5%, so the detection result shows that the designed system has stable performance and higher accuracy. Therefore, the weak photoelectric signal detection system designed in this research can detect the amplitude and frequency of weak photocurrent signals, and it has the higher detection accuracy.