Sonar Processing Unit Sidelobe Interference Reduction
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Solution Overview
Problem
Existing sonar systems face challenges in reliably distinguishing targets in secondary directions from those in the main direction due to the presence of sidelobes, which can amplify noise emissions, leading to inaccurate target separation.
Innovation Solution
The processing unit employs a fast Fourier transformation (FFT) to divide hydrophone signals into frequency bands, multiplies each band by specific factors, and uses an inverse FFT to transform back into time signals, allowing for precise compensation of transit time differences and improved target separation by generating frequency-selective direction-time signals. This method adapts factors based on hydrophone signal values and correlation, utilizing adaptive beamforming for optimal energy distribution and directional resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional beamforming with time delays is used, then directional signal processing is achieved, but target separation accuracy deteriorates due to sidelobe interference
Solution Approach 1:
The patent divides the frequency spectrum into multiple frequency bands and processes each band separately with different time delay coefficients. This segmentation allows the system to suppress sidelobes in specific frequency ranges while maintaining main lobe performance, thereby improving target separation accuracy without being overwhelmed by broadband sidelobe interference
Solution Approach 2:
The patent applies different time delay coefficients locally to different frequency bands rather than using a single set of coefficients for all frequencies. This local optimization enables precise control over the beamforming response in each frequency band, suppressing sidelobes where they cause interference while preserving signal strength in the main direction
2Use of energy by moving object
If frequency domain processing is used, then computing power demand is reduced, but target detection precision may deteriorate
Solution Approach 1:
The patent processes hydrophone signals in the frequency domain by dividing them into multiple frequency bands, applying FFT to convert time-domain signals to frequency-domain representation. This approach reduces the computational complexity compared to time-domain processing while maintaining sufficient precision through band-specific processing and adaptive coefficient adjustment
3Measurement precision
If adaptive beamforming is implemented, then target separation improves, but system complexity increases
Solution Approach 1:
The patent adjusts time delay coefficients adaptively for different frequency bands based on the spectral characteristics of the received signals. By changing the processing parameters (time delay coefficients) according to the specific frequency band and signal conditions, the system achieves improved target separation while keeping the overall system structure relatively simple
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 enhances target separation by precisely compensating transit time differences and adapting to environmental factors like water temperature and salinity, reducing sidelobe interference and improving the accuracy of target detection in sonar systems.
Implementation Method 1
The processing unit 10 comprises an FFT unit, namely a fast Fourier transformation unit (12), for determining Fourier-transformed hydrophone signals (16) from the supplied hydrophone signals (14)
Implementation Method 2
The processing unit 10 comprises an IFFT unit (22) for transforming the multiplied signals (21) back into time signals (24)
Implementation Method 3
Hydrophones convert waterborne sound into electrical signals, also called hydrophone signals
Data Source
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AI summary
The invention relates to a processing unit (10) for a sonar system for processing hydrophone signals (14). The processing unit (10) comprises an FFT unit (12) for determining a respective Fourier-transformed hydrophone signal (16) from each of the received hydrophone signals (14), as well as a frequency band divider (32) which divides each of the Fourier-transformed hydrophone signals (16) into multiple frequency bands. The processing unit (10) also comprises at least one multiplication unit (34a-34c) for determining multiplied signals (35) via the multiplication of every Fourier-transformed hydrophone signal of every frequency band (33a-33c) by a factor, at least one IFFT unit (36a-36c) for converting each of the multiplied signals (35) into a time signal, and at least one addition unit (41a-41c) for adding multiple or all of the time signals (38). The invention also relates to a sonar system for underwater vehicles, as well as to a method for processing hydrophone signals (14) using a processing unit (10).