Doppler Compensation for Underwater Acoustic Waveforms
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Solution Overview
Problem
Existing techniques for compensating for waveform distortion due to the Doppler effect in communication systems, particularly in water or through solid mediums, face accuracy issues when dealing with composite waves and changing receiver speeds.
Innovation Solution
A Doppler compensation system that includes a sound wave receiving element, a ground-speed-related quantity acquisition unit, an extraction unit, an arrival direction estimation unit, a reception-direction-speed-related quantity estimation unit, and a Doppler compensation unit, which work together to estimate and compensate for waveform distortions caused by the Doppler effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If unmodulated sound waves are transmitted for Doppler estimation, then the compensation process can be simplified, but the accuracy of waveform distortion compensation decreases when sound waves are strongly reflected or scattered on the sea surface
Solution Approach 1:
The patent segments the received composite sound wave into multiple individual plane waves through Fourier expansion. Each plane wave component is processed separately to calculate its specific Doppler shift amount, allowing accurate compensation even when waves arrive through different paths with different Doppler effects. This segmentation approach resolves the contradiction by maintaining simplicity in the overall process while achieving high accuracy through component-wise processing.
2Speed
If the receiver moves due to waves and sea surface fluctuations, then the Doppler shift amount changes quickly, but using traditional compensation techniques fails to accurately track these rapid changes
Solution Approach 1:
The patent implements a feedback mechanism where the receiver continuously monitors the received sound wave characteristics, calculates the current Doppler shift amount for each plane wave component, and adjusts the compensation parameters in real-time. This feedback loop enables the system to track rapid changes in receiver movement caused by waves and sea surface fluctuations, maintaining accurate Doppler compensation despite quick variations in motion state.
3Adaptability or versatility
If composite waves are used for communication, then different communication content can be transmitted, but the waveform becomes distorted due to individual frequency shifts of each plane wave
Solution Approach 1:
The patent applies local quality by treating each plane wave component in the composite wave differently. Instead of applying a uniform compensation to the entire composite wave, the system calculates and applies individual Doppler shift compensation to each frequency component based on its specific characteristics and propagation path. This allows the system to maintain waveform stability for communication while preserving the adaptability of using different composite waveforms for various communication contents.
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
The system effectively reduces the influence of the Doppler effect on communication by accurately estimating and compensating for waveform distortions, even in complex scenarios with composite waves and varying receiver speeds.
Implementation Method 1
communication using sound waves in water
Implementation Method 2
waveform distortion due to the Doppler effect may be a problem
Data Source
AI summary
An aspect of the present invention is a Doppler compensation system including: a sound wave receiving element that receives a sound wave transmitted by a transmitter; a ground-speed-related quantity acquisition unit that acquires a ground-speed-related quantity that is a physical quantity related to a vector representing a ground speed of a receiver including the sound wave receiving element based on an acceleration of the receiver; an extraction unit that extracts a sound wave including an estimation target sound wave that is a sound wave to be estimated from among sound waves received by the receiver; an arrival direction estimation unit that estimates an arrival direction of the estimation target sound wave based on the estimation target sound wave; a reception-direction-speed-related quantity estimation unit that estimates a quantity related to a speed in a reception direction that is a direction in which the estimation target sound wave viewed from the receiver arrives based on the ground-speed-related quantity and a result of the estimation from the arrival direction estimation unit; and a Doppler compensation unit that compensates for waveform distortion due to Doppler effect of the estimation target sound wave based on a result of the estimation from the reception-direction-speed-related quantity estimation unit.