Passive Sonar Ghost Source Elimination via Doppler Azimuth Analysis
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Solution Overview
Problem
Conventional passive sonar systems using linear antennas face ambiguity issues in determining the direction of incoming acoustic signals, leading to the presence of 'ghost sources' during source localization, which are costly to resolve due to the need for additional equipment and complex processing.
Innovation Solution
A procedure involving the acquisition of azimuth and frequency measurements from multiple linear antennas, followed by the determination of speed and frequency values to eliminate ambiguity through measurement equations and filtering methods, allowing for the identification of real sources and rejection of ghost sources without additional equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional passive linear antennas with omni-directional sensors are used, then the system cost is reduced and device complexity is lowered, but measurement precision deteriorates due to right/left ambiguity leading to ghost sources
Solution Approach 1:
The patent applies preliminary action by performing multiple measurements at different positions along the antenna before final source localization. The method accumulates angular measurements from multiple locations and uses statistical processing to resolve ambiguities before determining the final source position, thereby eliminating ghost sources while maintaining system simplicity
Solution Approach 2:
The patent resolves the two-dimensional angular ambiguity by introducing a temporal dimension through sequential measurements at different antenna positions. By moving the antenna to multiple locations and collecting angular data over time, the system transforms an ambiguous 2D localization problem into a resolvable multi-temporal measurement problem
2Measurement precision
If additional equipment such as directive sensors or multiple parallel antennas is added to eliminate ambiguity, then measurement precision improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent applies self-service by using the existing omni-directional sensors to perform multiple measurements at different positions. The system uses its own simple hardware capabilities, combined with sophisticated signal processing algorithms, to resolve ambiguities without requiring additional directive sensors or parallel antenna structures
Solution Approach 2:
The patent changes the operational parameters by varying the antenna position along its length and utilizing different sensor elements sequentially. This parameter variation allows the system to resolve angular ambiguities through temporal and spatial diversity rather than through hardware complexity
3Measurement precision
If multiple parallel linear antennas are used to eliminate right/left ambiguity, then measurement precision improves, but the number of hydrophones increases leading to higher manufacturing cost
Solution Approach 1:
The patent applies segmentation by dividing a single linear antenna into multiple functional segments that are activated sequentially at different positions. Instead of using multiple parallel antennas simultaneously, the system segments the measurement process in space and time, using one antenna to perform the work of multiple antennas
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 eliminates ambiguity and identifies real sources in underwater surveillance systems using conventional passive linear antennas, reducing costs and complexity by leveraging existing measurements and processing methods.
Implementation Method 1
comprise a set of omni-directional unit acoustic sensors or hydrophones located along the antenna
Implementation Method 2
an initial step (step 21) for acquisition of a frequency and bearing measurement of the signal received
Implementation Method 3
The signal received corresponds, to within the Doppler effect, to the signal emitted by the source(s) detected(s)
Implementation Method 4
A second step (step 22) for determination of the speed values corresponding to the different potential sources, and possibly the corresponding frequency f0 of the signal emitted by these sources. This estimation of the parameters characterizing the potential sources is made using the frequency values measured f(t i ) and azimuth values θ(t i ) measured during the first step (step 21) at different moments t i
Data Source
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AI summary
This invention concerns the field of passive sonar systems simultaneously processing several linear antennas. This invention consists mainly of a procedure for eliminating ghost sources for a passive sonar comprising at least two linear antennas A and B, with: An initial acquisition step (21) during which the signal received is measured at different moments of measurement ti, and for each antenna, the Doppler frequency f of the signal received is determined, as well as the possible values of the azimuth T of the source, A second step (22) for determining the potential values of the This step is performed using the measured azimuth source speed. frequency f values, A third step (23) eliminating ambiguity and rejecting ghost sources during which it is determined, for which of the potential sources, the speed and frequency values will satisfy, for each measurement moment ti, the measurement equations linking the frequency of the signal received to the frequency f0 emitted by the source, at the source speed and position. This invention mainly concerns harbor surveillance systems comprising several passive linear antennas laid on the seabed and located around the roadstead.