The applications of fractional Fourier transform in underwater acoustic trajectory tracking

As an important kind of non-stationary signals, the linear frequency modulation signals have been widely used in underwater acoustic communication systems and signal detection systems. The fractional Fourier transform is an effective transform manner to analyse non-stationary signals especially to detect linear frequency modulation signals. The time measurement manner can be changed into frequency measurement manner by employing fractional Fourier transform to detect linear frequency signals. In the receiver, we acquire time domain data of transmitted signal by measuring u-domain peak position of detected signal. Then we can find the beginning of transmitted signal. To enhance the time measurement precision of this manner, we truncate some points of transmitted signal in the transmitter to make the u-domain peak position shift susceptive. This paper mainly simulates target trajectory tracking under underwater acoustic condition. We overlap several truncated linear frequency modulation signals to transmit. Using the fractional Fourier transform to detect linear frequency modulation signals, to acquire the time delay between targets and transducer arrays. Target bearing is resolved by hyperboloid intersection algorithm to track trajectory of the target.