Improved space time prewhitener for linear frequency modulation reverberation using fractional Fourier transform

Area of Science:

• Signal Processing
• Acoustics
• Sonar Technology

Background:

• Reverberation significantly degrades active sonar detection performance, especially in shallow waters.
• Linear frequency modulation (LFM) signals are commonly used in active sonar but are susceptible to reverberation.
• Existing prewhitening methods struggle to effectively address LFM reverberation.

Purpose of the Study:

• To develop an improved space-time prewhitening method for LFM reverberation.
• To enhance the detection capabilities of active sonar systems operating in shallow marine environments.
• To address the limitations of current methods in handling complex reverberation scenarios.

Main Methods:

• The proposed method utilizes the fractional Fourier transform to map LFM reverberation into the fractional Fourier domain.
• In this domain, the reverberation is whitened by focusing the linearly varying frequency onto a stationary frequency.
• Adjacent signal blocks are employed as reference signals for the prewhitening process.

Main Results:

• The fractional Fourier transform effectively focuses the LFM reverberation.
• The prewhitening process in the fractional Fourier domain significantly reduces reverberation.
• Experimental results demonstrate a substantial improvement in active sonar detection performance in shallow seas.

Conclusions:

• The proposed space-time prewhitening method offers a significant advancement for active sonar in shallow waters.
• Transforming LFM reverberation to the fractional Fourier domain is an effective strategy for signal whitening.
• The method shows practical utility and improved performance with real reverberation data.