Correlation Detection Of Weak Laser Pulse Signal

The dissertation needs to detect laser pulse signal which has been submerged in noise, and to realize improvement of signal-to-noise ratio (SNR), at last, to construct a high-sensitive detection system.We receive the laser pulse signal with the binary photo-electric detector, then, deal the signal with the circuit that is designed on the basis of the principle of correlation detection to improve signal-to-noise ratio (SNR). By analyzing the properties of the noise and pulse signal, we conclude signal is correlated to itself but not correlated to noise, and noise itself is not correlated. According to the properties of signal and noise, we detect the weak laser pulse signal using the technique of correlation detection to reject noise and enhance signal-to-noise ratio (SNR). The main work of the dissertation lies in: according to the principle correlation detection and using Simulink simulate, the simulated results show signal-to-noise ratio (SNR) of the output signal has achieved 6.98dB and 20.43dB as a result of pressing of correlation detection systems with the signal-to-noise ratio (SNR)of input signal are -4.44dB and 1.02dB, respectively. The signal has been highlighted and therefore, we can distill the desired signal. The simulated results confirm the signal detection system being designed on the basis of the principle of correlation detection can deal with weak laser pulse signal and furthermore, the signal-to-noise ratio (SNR). We design the correlation detection circuitry to detect weak signal. Signal-to-noise ratio (SNR) of the output signal achieves 29.1dB and signal-to-noise improvement ratio (SNIR) achieves 35.54dB while signal-to-noise ratio (SNR) of input signal is -6.44dB. Such results can satisfy the much requirement. In view of delay time may eliminate noise, we have experimented on different delay time. Because the width of pulse signal is only about 15ns, the choice scope of delay time is very small, so experimentation has been development via selecting delay time: 0ns, 3ns, 5ns, and 7ns. The experimentation results show the capability of detection system is different when select the different delay time. Signal-to-noise ratio (SNR) of output signal degrades and the capability of detection system is down resulting from increasing the delay time, but change is not especially conspicuous and can been believed to be almost uniform. Thus, we can confirm the delay time is not useful to enhance systems performances.The simulated results and experiment have proved that the correlation detection can been used to detect weak pulse signal. At last, we have designed the correlation detection circuitry for engineering applications.