Pseudo Noise Echo Sounding Horizontal Resolution
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Solution Overview
Problem
Conventional echo sounding apparatuses face limitations in resolving the horizontal direction due to a restricted transmitting period, which affects measurement resolution and accuracy, and require acceleration sensors for ship motion detection, increasing costs and error risks.
Innovation Solution
The use of a pseudo noise sequence generating circuit to form transmission signals, allowing for shorter transmitting periods and accurate ship motion correction without acceleration sensors, by correlating echo signals with pseudo noise sequences to determine time differences and improve signal resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the transmitting period is extended to allow echo reception, then the depth measurement range is improved, but the horizontal resolution deteriorates due to ship movement
Solution Approach 1:
The patent divides the wide beam into multiple narrow sub-beams using a beam separation unit. This segmentation allows the system to measure depth across a wide range while maintaining high horizontal resolution, as each sub-beam provides precise depth information for its specific angular sector, eliminating the trade-off between range and resolution.
Solution Approach 2:
The patent introduces angular dimension by separating the beam into multiple directions. Instead of measuring depth in a single direction, the system measures depth in multiple angular directions simultaneously, transforming a one-dimensional depth measurement problem into a two-dimensional (angle-depth) measurement problem, thereby achieving both wide coverage and high resolution.
2Measurement precision
If acceleration sensors are used for ship motion detection, then the measurement accuracy is improved, but the device complexity and cost increase
Solution Approach 1:
The patent uses the echo sounding system itself to detect ship motion. By analyzing variations in echo signals caused by ship movement, the system self-diagnoses motion effects and performs correction without external sensors. This eliminates the need for acceleration sensors while maintaining measurement accuracy.
Solution Approach 2:
The patent uses echo signals as an intermediary to detect ship motion. Instead of directly measuring ship motion with sensors, the system uses the interaction between sound waves and the moving platform as a mediator to infer motion characteristics, which are then used to correct depth measurements.
3Manufacturing precision
If the transmitting period is shortened to improve horizontal resolution, then the measurement resolution is improved, but the echo reception becomes unreliable due to overlapping pulses
Solution Approach 1:
The patent segments the transmitted beam into multiple narrow sub-beams. This allows the system to transmit pulses more frequently (shorter period) while maintaining reliable echo reception, because each narrow sub-beam has a smaller spatial footprint and less likely to cause pulse overlap confusion. The segmentation effectively reduces the interference between consecutive pulses.
Solution Approach 2:
The patent changes the beam width parameter by separating it into multiple narrow beams. This parameter change allows the system to operate with shorter transmitting periods while maintaining reliable echo detection, as the narrow beams provide clearer temporal separation of echoes even at higher pulse repetition frequencies.
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 enables higher resolution in the horizontal direction, accurate ship motion detection and correction, and reduces costs by eliminating the need for acceleration sensors, while improving signal-to-noise ratio and enabling miniaturization and power efficiency in the apparatus.
Implementation Method 1
An ultrasonic pulse is generated from an ultrasonic transducer, an echo obtained when its sound wave is reflected from a target (sea bottom) is captured
Implementation Method 2
an echo obtained when its sound wave is reflected from a target (sea bottom) is captured
Implementation Method 3
an echo obtained when its sound wave is reflected from a target (sea bottom) is captured
Implementation Method 4
a pseudo noise sequence generating circuit for generating a pseudo noise sequence signal and a modulating circuit for forming a transmission signal by modulating a carrier signal with the pseudo noise sequence signal
Data Source
AI summary
An echo measuring apparatus has: a transmission signal forming unit for forming a transmission signal by a pseudo noise sequence signal; a transmitting unit for transmitting the transmission signal as an ultrasonic wave into the water; a receiving unit for receiving an echo of the ultrasonic wave; and a correlator for discriminating the echo corresponding to the transmission signal by executing a correlating process to the echo by the pseudo noise sequence signal and measuring a distance to a measurement target on the basis of a time difference between the transmission signal and the echo, wherein assuming that a velocity of a sound wave in the water is equal to Vu and the distance to the measurement target is equal to D, a period of the transmission signal includes a case where it is equal to or less than (2D/Vu).