Improvement of the signal to noise ratio of Lidar echo signal based on wavelet de-noising technique

According to the characteristics of a Lidar echo signal contaminated by noise, especially in strong background light, an effective de-noising method of wavelets based on a soft threshold is proposed to reduce the Lidar echo signal noise and improve the signal to noise ratio of system. The principles and methods of wavelet transforms and wavelet de-noising are utilized to de-noise the noisy signals. Some preliminary simulations are carried out to reduce the noise of the simulated signals in order to verify the feasibility of the de-noising method. In addition, using experimental data of the Lidar echo signals contaminated by noise in the strong background light, the de-noising range-square-corrected signals and the retrieved aerosol extinction coefficient are obtained. The results show evidence of the de-noising effects and demonstrate that this method can effectively de-noise the noisy Lidar signals in strong background light and achieve improvement in the signal to noise ratio of system. ► The algorithms of wavelet transforms and wavelet de-noising are illustrated. ► The characteristics of Lidar echo signal with the noises are described. ► The steps of Lidar echo signal noise removal are demonstrated. ► Lidar echo signals taken during daytime are de-noised effectively in practice. ► Extinction coefficients of original signal and de-noised signal are compared.