SEApara is a novel, low-logistic sub-bottom profiling system currently in development specifically for deployment on subsea remotely operated and autonomous vehicles (ROV and AUV). It is a highly efficient and compact sub-bottom profiler using parametric array technology and chirp waveforms to achieve high resolution and deep penetration with a small transducer and low power consumption.
The SEApara system comprises sonar transducers, an electronics unit and interfaces for communicating with the vehicle and data retrieval. Data are stored in industry standard formats for uploading after a mission to any third party display and analysis software packages.
Parametric Array
SEApara is a monostatic parametric array sonar system whereby two signals are transmitted at high frequencies and non-linear interaction generates distortion products at the sum and difference of these frequencies. It is the difference frequency (secondary frequency) signal that is generally of interest. This signal is created throughout a volume in front of the transducer where the primary frequency beams interact, and this source volume acts as a virtual line array source for the difference frequency. This in turn creates a narrow directional beam at the secondary frequency. With appropriate design parameters, this enables high directivity at low frequencies from a small transmission aperture, with low side lobes and wide bandwidth. Primary and secondary echoes are received, digitised, detected and stored separately.
Technical Specifications
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TRANSMITTER
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Primary Frequency
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~100 kHz
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Array Size
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10 cm diameter
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Primary Source Level
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220 dB re 1µPa@1 m
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Primary Beamwidth
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8.9°
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Peak Power
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100 W
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Secondary Centre Frequency
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16 kHz
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Bandwidth
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28 kHz
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Pulse type
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Chirp/Ricker/Custom
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Secondary Equivalent Source Level
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178 dB re 1µPa@1 m
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Secondary Beamwidth
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2.9°
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Pulse Length
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~5 ms
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Pulse Repetition Frequency
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2.5 per sec
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RECEIVER
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Low Frequency Receiver
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Omni-directional hydrophone
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High Frequency Receiver
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HF Transmitter
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PERFORMANCE
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Vertical Resolution
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3 cm
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Penetration
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Sand: Altitude 10 m 9 m
Altitude 20 m 6 m
Altitude 50 m 4 m
Clay: Altitude 10 m 45 m
Altitude 20 m 26 m
Altitude 50 m 12 m
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Mean power consumption
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<30 W
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