Sonar Target Characterization and Echo Separation Using the Fractional Fourier Transform and its Relation to the Wigner Distribution
Journal Title: International Journal of engineering Research and Applications - Year 2017, Vol 7, Issue 8
Abstract
In this paper, we apply the relationship between the Fractional Fourier Transform (FrFT) and the Wigner Distribution (WD) to identify and separate echoes from an active sonar based upon the characteristics of different targets. Plotting the received echo using the WD, which is a time-frequency plane representation, allows us to identify the characteristics of the environment, since targets will have different time and frequency domain responses to the chirp or tone pulses that will manifest in the WD. A chirp (or tone) can also be easily separated from the cluttered background, hence enabling extraction of targets, such as submarines, from the clutter. The received signal is rotated to a new time axis „ta‟, with rotational parameter „a‟, such that the chirp becomes a tone and can be extracted or notched easily, without requiring a filter. Echoes with just slight differences in Doppler can be easily separated. Furthermore, echoes from strong targets, such as submarines, can be easily notched to extract the weaker targets, such as schools of fish. We demonstrate the algorithm by simulation, using several target types and chirp or tone transmit pulses. We show that a weak signal up to 20 dB below a strong one can be easily extracted using the FrFT by notching the strong target first.
Authors and Affiliations
Seema Sud
Keywords
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- EP ID EP391961
- DOI 10.9790/9622-0708028690.
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