Acoustic Positioning via Phase Difference Measurement
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Solution Overview
Problem
Existing acoustic positioning methods face limitations in accuracy, range, complexity, and size of antennas, particularly requiring high-frequency signals that reduce range and necessitate large, complex multi-receiver antennas, and cannot position a mobile in a passive and discrete manner.
Innovation Solution
An acoustic positioning system that emits a sequence of two acoustic signals of the same central frequency, separated by a determined time interval, using asynchronous clocks to measure the phase of arrival of these signals, allowing for accurate relative displacement calculation independent of distance with small-size and low-cost elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-frequency acoustic signals are used to improve positioning accuracy, then measurement precision is improved, but range is reduced due to poor propagation of high-frequency waves
Solution Approach 1:
The system emits periodic acoustic signals at a fixed frequency (e.g., 10 kHz) rather than using wide-band high-frequency signals. By using periodic continuous waves with a determined frequency and time interval between emissions, the system achieves accurate phase difference measurements without the range limitations of high-frequency wide-band signals.
Solution Approach 2:
The invention changes the fundamental parameter from wide-band high-frequency signals to narrow-band periodic signals at a specific frequency. This parameter change allows the system to achieve positioning accuracy through phase difference measurement while maintaining good signal propagation over long ranges, as the lower frequency periodic signals experience less attenuation.
2Measurement precision
If multi-receiver antennas are used to measure phase differences for positioning, then measurement precision is improved, but device complexity and antenna size increase
Solution Approach 1:
The system segments the positioning function by using a single receiver that sequentially processes signals from different emitters or time intervals, rather than requiring all receivers to operate simultaneously. This segmentation allows accurate phase difference measurement without the complexity of a full multi-receiver array operating at once.
Solution Approach 2:
By using periodic signal emissions with determined time intervals, the system can use a single receiver to measure phase differences sequentially. The periodic nature of the signals allows the receiver to identify and measure phase differences from multiple emitters or transmission events without requiring multiple simultaneous receivers, thus reducing device complexity while maintaining positioning accuracy.
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
Achieves positioning accuracy to a fraction of the acoustic wavelength, independent of distance, using simple and cost-effective components, and enables passive positioning without emitting acoustic waves, significantly improving range and reducing antenna complexity.
Implementation Method 1
measuring a relative displacement of a mobile with respect to one or several reference, this measurement being based on the transmission of acoustic signals between the mobile and the reference(s)
Implementation Method 2
acoustic reception means operable to receive and to measure the phase of arrival of these signals
Data Source
AI summary
An acoustic positioning device includes an acoustic emitter and receiver. The device emits a sequence of at least one first acoustic signal (S1) and one second acoustic signal (S2), separated by a time interval T, and to receive and measure the arrival phase φ1 of S1 and the arrival phase φ2 of S2. The device measures a relative displacement between the acoustic emitter and the acoustic receiver and determines the approximate difference (R2−R1)AUX between the distance R1 traveled by S1 between the acoustic emitter and receiver, and the distance R2 traveled by S2 between the acoustic emitter and the acoustic receiver, and calculates the relative displacement (R2−R1) between the acoustic emitter and the acoustic receiver as a function of the approximate difference (R2−R1)AUX, of the time interval T and of the arrival phases φ1, φ2 respectively of S1 and of S2.