Forward Scattered Wave Target Detection in Complex Underwater Environments
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Solution Overview
Problem
Current target detection methods using time reversal waves require repeated processing and struggle to discriminate between targets, especially when they are close in size or obscured by obstacles, and are influenced by sea surface and seabed reflections, making it difficult to detect targets in complex underwater environments.
Innovation Solution
A target detection device and method that utilizes forward scattered waves instead of backward scattered waves, employing vector addition processing to isolate and time-reverse the forward scattered waves, with phase conjugation determination to ensure accurate targeting in complex environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If backward scattered waves are used for target detection with time reversal processing, then target detection capability is achieved, but detection time becomes excessively long due to repeated processing requirements
Solution Approach 1:
The patent inverts the conventional approach by using forward scattered waves instead of backward scattered waves. The transducer array receives forward scattered waves that propagate in the same general direction as the incident wave, rather than receiving backward scattered waves that reflect toward the source. This inversion of the detection direction eliminates the need for repeated time reversal processing while maintaining target detection capability.
Solution Approach 2:
The patent performs preliminary signal processing by extracting the forward scattered wave signal from the total received signal before time reversal processing. The extraction unit separates the forward scattered wave component from other signals in advance, so that subsequent time reversal processing only needs to be applied once to the already-isolated target signal, significantly reducing total detection time.
2Loss of energy
If low frequency sonic waves are used to extend detection distance, then absorption attenuation is reduced, but the sonic beam widens and reflection influences from sea surface and seabed increase
Solution Approach 1:
The patent extracts the forward scattered wave signal from the composite received signal using signal processing techniques. By separating the forward scattered wave component from direct waves, reflected waves, and other interference signals, the system can use low frequency waves for extended detection distance while removing the harmful reflection components through extraction processing.
Solution Approach 2:
The patent changes the frequency parameter of the sonic waves to low frequency (such as 500 Hz) to reduce absorption attenuation and extend detection distance. Although this causes beam widening and increased reflections, the forward scattered wave extraction technique selectively isolates the target signal at this low frequency, maintaining detection precision despite the parameter change.
3Measurement precision
If repeated time reversal processing is applied to backward scattered waves, then target convergence is achieved, but processing complexity and time requirements increase tremendously
Solution Approach 1:
The patent performs preliminary extraction of the forward scattered wave signal before time reversal processing. By isolating the target-related signal component in advance through the extraction unit, the system requires only a single time reversal processing operation rather than repeated processing, significantly reducing computational complexity while maintaining convergence precision.
4Loss of time
If forward scattered waves are used instead of backward scattered waves, then detection time is reduced and accuracy is improved, but signal extraction from complex sound fields becomes more difficult
Solution Approach 1:
The patent introduces an extraction unit as an intermediary component between the transducer array and the time reversal processing unit. This intermediary performs signal separation and extraction of the forward scattered wave component from the composite sound field, facilitating the transition from raw received signals to isolated target signals in a systematic manner.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for efficient detection of targets in shaded regions and behind obstacles, reducing detection time and improving accuracy by isolating and converging forward scattered waves to their precise location, even in environments with obstacles.
Implementation Method 1
a sound source which projects a sound pulse within the propagation environment
Implementation Method 2
a forward scattered wave scattered forward from the target
Implementation Method 3
a transducer array disposed in a region for receiving a forward scattered wave
Implementation Method 4
an addition processing unit which extracts only a signal of the forward scattered wave by applying vector addition processing
Implementation Method 5
a phase conjugation determination unit which checks whether or not a phase conjugacy is established in the propagation environment from the sound source to the transducer array by receiving the signal of the forward scattered wave extracted by the vector addition processing performed by the addition processing unit and employing a passive phase conjugation
Implementation Method 6
a time reversal processing unit which generates a time-reversed time reversal signal by applying time reversal processing on the forward scattered wave
Data Source
AI summary
A target detection device includes: a sound source which projects a sound pulse; a transducer array disposed in a region for receiving a forward scattered wave from an object in the propagation environment; an addition processing unit which extracts only a signal of the forward scattered wave by applying vector addition processing on a reference signal in a reference sound field received when an obstacle exists in the propagation environment and a mixed signal in a mixed sound field received when the target exists with the obstacle; a phase conjugation determination unit which checks whether a phase conjugacy is established by receiving the signal of the extracted forward scattered wave and employing a passive phase conjugation for determining the reference sound field; and a time reversal processing unit which generates a time reversal signal on condition that the phase conjugation determination unit judges that the phase conjugacy is established.