Line spectrum tracking control based on the method of biorthogonal demodulation

The low-frequency characteristic line spectrum contains significant information about underwater targets, which makes both its detection and control a hot topic of research. Attempts to suppress the characteristic line spectrum by active control strategy are greatly influenced by the tracking effect of the instantaneous information of the line spectrum, and have to deal with two specific technical problems in underwater applications. Firstly, the instability of the line spectrum; and, secondly, uncertain compensation of time delay, which is closely related to hydrological parameters. In order to cope with these problems, a tracking control strategy was proposed. This idea is based on biorthogonal demodulation, by smoothing phase-difference and cross-correlation time-delay estimation. This makes it possible to track the phase and frequency information of a signal. Secondly, the performance of the tracking algorithm for several typical models of signals under additive Gaussian white noise environment was simulated, and the accuracy of the tracked instantaneous information was given. Thirdly, the factors influencing the performance of the algorithm are discussed and the measures to improve accuracy are introduced. Finally, the effectiveness of the proposed strategy was confirmed through the validation of the measured data obtained by an experiment.