Electronic Baffling of Sensor Arrays for Back-Lobe Noise Rejection
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Solution Overview
Problem
Conventional sonar arrays mounted on vessels face challenges in rejecting unwanted noise components detected through the ambiguous back-lobe, which are not effectively attenuated by traditional mechanical baffling methods, especially at low frequencies, due to the limitations of baffle thickness and weight considerations.
Innovation Solution
Combining the outputs of hydrophones and pressure-gradient sensors within the same array to form cardioid beams with nulls pointing in the ambiguous beam-steer directions, allowing for the reduction of noise components from the hull of a vessel without the need for mechanical baffling, by deriving and scaling signals from each sensor group to cancel out back-lobe noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If mechanical baffles are made thick to effectively decouple sensors from hull vibrations at low frequencies, then noise attenuation is improved, but weight and cost increase significantly
Solution Approach 1:
The patent replaces the mechanical baffle system with an electronic signal processing system. Instead of using physical barriers to block noise, the invention uses electronic techniques to identify and cancel noise signals detected by the array, thereby achieving noise attenuation without the weight and cost penalties of thick mechanical baffles
Solution Approach 2:
The patent changes the approach from physical parameter modification (baffle thickness) to signal parameter processing. By analyzing and manipulating the temporal and spectral characteristics of detected signals, the system can distinguish and attenuate noise components without requiring physical decoupling structures
2Object-affected harmful factors
If mechanical baffles are used to isolate sensors from hull vibrations, then noise rejection is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical baffle system with an electronic signal processing system. Instead of using physical barriers to block noise, the invention uses electronic techniques to identify and cancel noise signals detected by the array, thereby achieving noise attenuation without the weight and cost penalties of thick mechanical baffles
Solution Approach 2:
The noise cancellation system uses the array's own detected signals to identify and cancel noise components. The system processes the signals from the array elements, identifies noise patterns, and applies cancellation techniques using the array's existing infrastructure, eliminating the need for separate mechanical decoupling systems
3Measurement precision
If conventional beamforming is used, then directional signal detection is achieved, but back-lobe noise cannot be rejected
Solution Approach 1:
The patent segments the beamforming process into multiple stages: conventional beamforming to establish directional responses, followed by a separate noise cancellation stage that processes the beamformed outputs. This segmentation allows the system to maintain directional detection capabilities while adding specific functionality to reject back-lobe noise through adaptive filtering and signal subtraction techniques
Solution Approach 2:
The patent implements feedback mechanisms where the detected signals are processed to identify noise components, and the cancellation results are fed back to refine the beamforming outputs. This feedback loop enables continuous optimization of noise rejection while preserving the directional detection characteristics of the original beamformed signals
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 effectively minimizes noise from the back-lobe, improving noise rejection without the weight and cost penalties of thick mechanical baffles, while maintaining effective noise attenuation across a range of frequencies.
Implementation Method 1
hydrophones that sense pressure
Implementation Method 2
pressure-gradient sensors, deployed within the same array, that measure the pressure gradient
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
A method and system is described for reducing unwanted noise components/interfering targets detected through an ambiguous beam-steer direction, such as the ambiguous `back-lobe' of a sensor array. A pressure sensor array 52 and a plurality of pressure gradient sub-arrays 541-N are beamformed individually at processing stages 56, 581-N to derive signals indicative of directional responses, one from each group or sub-group. The signals are scaled and weighted (60, 620-N) and processed to define a cardioid beam with nulls pointing in the ambiguous beam-steer direction.