Academician Li creatively applied information theory, digital signal processing and underwater acoustic engineering to solve a series of problems in underwater acoustic signal processing, and made important contributions to the modernization of China's naval sonar equipment. In this paper, the steady-state characteristics of adaptive beamforming are studied, and the expression of solving beam directivity by using the optimal transfer function in frequency domain is given. The gain calculation method of detecting weak signals under the background of marine noise is given, which solves the problem that the classical theory needs to be corrected by the non-stationary noise field in time and the non-uniform noise field in space, and puts forward a new sonar equation expression, which is an important basis for guiding sonar design.
In the passive detection of underwater targets, a new method of estimating the target azimuth by using the phase information of acoustic signals and a new algorithm of completely separating multiple non-overlapping point source signals in space by using adaptive array processing method are proposed. In the design of digital sonar, technologies such as dynamic beamforming, programmable digital filtering, variable sampling rate operation, Kalman-like filtering, and gray scale transformation are put forward for the first time, and a simple underwater target recognition expert system is designed through cluster analysis, which has played a very good role in promoting the development of digital sonar in China.
1997 was elected as an academician of China Academy of Sciences. From 1984 to 1986, I worked in the United States for nearly two years at the invitation of Princeton University. 1976 participated in adaptive filtering research and won the first prize of major scientific and technological achievements of Chinese Academy of Sciences; 1978 participated in the research of 00 1 shore-based sonar station and won the first prize of the National Science Conference; 1984 was responsible for the development of 262 sonar, and won the scientific and technological progress award of the Sixth Machinery Division.
He has published dozens of papers, including Computer Simulation Technology in Sonar Design and Adaptive Array Signal Separation Theory. Monographs include Design Principle of Digital Sonar, Introduction to Sonar Signal Processing and Computer Graphics (co-edited).
On April 26th, 2007, the reporter of Science and Atheism interviewed Li, an academician of China Academy of Sciences. Academician Li is an expert in underwater acoustic signal processing and sonar design. He has been engaged in signal processing and sonar design and development for many years, and was the director of Institute of Acoustics, Chinese Academy of Sciences. In the long-term scientific research work, Academician Li deeply realized that scientific research should first have a scientific attitude, and only with a scientific attitude can research be carried out. Secondly, science needs truth, and science cannot be adulterated. Because what is truly scientific needs to be tested by practice.