A Study On Instantaneous Parameter Sequence Analysis Of Echoes And Its Application

The basic tasks of signal processing unit (SPU), the kernal part of modern sonar, include signal detection, parameter estimation, and target recognition or classification. they are broken up into three independent parts in the conventional signal processing theory and accomplished in turn in practice. The well development of microelectronics and high-speed dedicated digital signal processing (DSP) devices, has provided a suitable hardware environment for the united processor which merges (combines) detection, estimation and recognition. Preceeding with the instantaneous parameter estimation of active sonar's echo signal, this dissertation introduces two signal analysis methods(instantaneous frequency sequence analysis and pseudo bearing sequence analysis) and probes into the feasibility, physical foundation for constructing a united processor as the proceeding mentioned with them. The property analysis is also provided.The concept of "instantaneous frequency(IF)" introduced from the analysis of frequency modulated signal has provided a powerful tool for the analysis of unstationary signal. However, up to now the research on instantaneous parameters of signal in the literatures still concentrate on the same topic " instantaneous frequency(IF)", particularly focus upon the methods of IF estimation. The application research is often confined in some rather ideal occasions with extremely high signal-to-noise ratio(SNR) in ranging of seism and physiology signal analysis. Is the IF researches meaningful for signal detection, target recognition (or classification), besides parameter estimation? Is it potentially useful in lower SNR situations? How about other instantaneous parameters? This dissertation intends to study and reply these questions.The major contributions are as follow:Research on the algorithms of instantaneous frequency estimation. Several computationally/statistically efficient instantaneous frequency estimation algorithms are derived.Analysis of instantaneous frequency sequence and its statistical characteristics. Study on the relation of instantaneous frequency sequence analysis and the conventional Fourier spectrum analysis. Link of their lower moments is examined.Study on probability distributions of instantaneous frequency and variance of instantaneous frequency sequence.Probe into application of the presented instantaneous frequency sequence analysis method in signal detection areas. A new type of detector for norrowband signal—Variance of Instantaneous Frequency Detector(VIFD) is proposed in this dissertation. Its property is also evaluated through theoritical analysis and simulation.In the stationary Gaussian white noise background, the performance of VIFD in narrowband signal detection approaches that of the optimal detectors (matched filter or replica correlator). However,VIFD is more robust. it is superior to matched filter and conventional energy detector in detection ability in unstationary interference background, and it is insensitive to frequency mismatch caused by Doppler frequency shift.A new concept "pseudo bearing" and a new signal analysis method—pseudo bearing sequence analysis is presented. The probability distribution model of pseudo bearing, the theoritical foundation of pseudo bearing sequence analysis, and its realization and application in practical occasions such as detection, arti-reverberation, target size recognition are discussed. It is beneficial to systems with short arrays and wide beams.Another new detector based upon instantaneous parameter estimation is presented, which is named as variance-of-pseudo-bearing detector(VPBD). VPBD runs better than traditional detectors and VIFD in wide-beam systems.A precise realtime system for tracking underwater targets is developed with dual main processors TMS320C30. This system has the advantage of multibeam system at farther working distance, the advantage of long-baseline locating system in precision, and the advantage of short-base-line and ultrashort-base-line system in size of arrays, convenience and flexibility for use.Theoriticai analysis and computer simulation have proved the rationality of both instantaneous frequency sequence analysis method and pseudo bearing sequence analysis method. A trial at sea and trial data analysis confirmed the vilidity of the proposed methods.As a new technique, it is expected that the proposed methods in this dissertation might be found widely practical use in narrowband signal detection in unstationary background, torpedo target size recognition, underwater acoustic locating and tracking, and other areas.