A bat-like sonar system consisting of hardware digital correlators

2002 ◽  
Author(s):  
K. Nakahira ◽  
T. Kodama ◽  
T. Furnhashi ◽  
H. Maeda
Keyword(s):  
Sonar System

Embedded Air-Coupled Ultrasonic 3D Sonar System with GPU Acceleration

2020 ◽  
Author(s):  
Gianni Allevato ◽  
Matthias Rutsch ◽  
Jan Hinrichs ◽  
Marius Pesavento ◽  
Mario Kupnik
Keyword(s):  
Gpu Acceleration ◽  
Sonar System

Wave Breaking Dissipation in a Young Wind Sea

2014 ◽  
Vol 44 (1) ◽  
pp. 104-127 ◽  
Author(s):  
Michael Schwendeman ◽  
Jim Thomson ◽  
Johannes R. Gemmrich
Keyword(s):  
Wind Waves ◽  
Phase Speed ◽  
Field Studies ◽  
Turbulent Energy ◽  
Strength Parameter ◽  
Video Recordings ◽  
Sonar System ◽  
Wind Sea ◽  
Equilibrium Range

Abstract Coupled in situ and remote sensing measurements of young, strongly forced wind waves are applied to assess the role of breaking in an evolving wave field. In situ measurements of turbulent energy dissipation from wave-following Surface Wave Instrument Float with Tracking (SWIFT) drifters and a tethered acoustic Doppler sonar system are consistent with wave evolution and wind input (as estimated using the radiative transfer equation). The Phillips breaking crest distribution Λ(c) is calculated using stabilized shipboard video recordings and the Fourier-based method of Thomson and Jessup, with minor modifications. The resulting Λ(c) are unimodal distributions centered around half of the phase speed of the dominant waves, consistent with several recent studies. Breaking rates from Λ(c) increase with slope, similar to in situ dissipation. However, comparison of the breaking rate estimates from the shipboard video recordings with the SWIFT video recordings show that the breaking rate is likely underestimated in the shipboard video when wave conditions are calmer and breaking crests are small. The breaking strength parameter b is calculated by comparison of the fifth moment of Λ(c) with the measured dissipation rates. Neglecting recordings with inconsistent breaking rates, the resulting b data do not display any clear trends and are in the range of other reported values. The Λ(c) distributions are compared with the Phillips equilibrium range prediction and previous laboratory and field studies, leading to the identification of several inconsistencies.

scholarly journals Smart Ocean: A New Fast Deconvolved Beamforming Algorithm for Multibeam Sonar

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 4013 ◽  
Author(s):  
Jie Huang ◽  
Tian Zhou ◽  
Weidong Du ◽  
Jiajun Shen ◽  
Wanyuan Zhang
Keyword(s):  
High Frequency ◽  
Real Data ◽  
Side Lobe ◽  
Tunnel Effect ◽  
Computation Complexity ◽  
Acoustic Image ◽  
Multibeam Sonar ◽  
Sonar System ◽  
Topographic Survey ◽  
Beamforming Algorithm

A new fast deconvolved beamforming algorithm is proposed in this paper, and it can greatly reduce the computation complexity of the original Richardson–Lucy (R–L algorithm) deconvolution algorithm by utilizing the convolution theorem and the fast Fourier transform technique. This algorithm makes it possible for real-time high-resolution beamforming in a multibeam sonar system. This paper applies the new fast deconvolved beamforming algorithm to a high-frequency multibeam sonar system to obtain a high bearing resolution and low side lobe. In the sounding mode, it restrains the tunnel effect and makes the topographic survey more accurate. In the 2D acoustic image mode, it can obtain clear images, more details, and can better distinguish two close targets. Detailed implementation methods of the fast deconvolved beamforming are given, its computational complexity is analyzed, and its performance is evaluated with simulated and real data.

scholarly journals Code Optimisation Framework for Multicode Sonar Systems

2021 ◽  
Author(s):  
◽  
Muhammad Rashed
Keyword(s):  
Transmission Loss ◽  
Matched Filter ◽  
Signal To Noise Ratio ◽  
Welch Bound ◽  
Optimisation Algorithm ◽  
Sonar System ◽  
Channel Effects ◽  
Sonar Systems ◽  
Mismatched Filters ◽  
Quadratically Constrained

<p>The ocean is a temporally and spatially varying environment, the characteristics of which pose significant challenges to the development of effective underwater wireless communications and sensing systems.  An underwater sensing system such as a sonar detects the presence of a known signal through correlation. It is advantageous to use multiple transducers to increase surveying area with reduced surveying costs and time. Each transducers is assigned a dedicated code. When using multiple codes, the sidelobes of auto- and crosscorrelations are restricted to theoretical limits known as bounds. Sets of codes must be optimised in order to achieve optimal correlation properties, and, achieve Sidelobe Level (SLL)s as low as possible.  In this thesis, we present a novel code-optimisation method to optimise code-sets with any number of codes and up to any length of each code. We optimise code-sets for a matched filter for application in a multi-code sonar system. We first present our gradient-descent based algorithm to optimise sets of codes for flat and low crosscorrelations and autocorrelation sidelobes, including conformance of the magnitude of the samples of the codes to a target power profile. We incorporate the transducer frequency response and the channel effects into the optimisation algorithm. We compare the correlations of our optimised codes with the well-known Welch bound. We then present a method to widen the autocorrelation mainlobe and impose monotonicity. In many cases, we are able to achieve SLLs beyond the Welch bound.  We study the Signal to Noise Ratio (SNR) improvement of the optimised codes for an Underwater Acoustic (UWA) channel. During its propagation, the acoustic wave suffers non-constant transmission loss which is compensated by the application of an appropriate Time Variable Gain (TVG). The effect of the TVG modifies the noise received with the signal. We show that in most cases, the matched filter is still the optimum filter. We also show that the accuracy in timing is very important in the application of the TVG to the received signal.  We then incorporate Doppler tolerance into the existing optimisation algorithm. Our proposed method is able to optimise sets of codes for multiple Doppler scaling factors and non-integer delays in the arrival of the reflection, while still conforming to other constraints.  We suggest designing mismatched filters to further reduce the SLLs, firstly using an existing Quadratically Constrained Qaudratic Program (QCQP) formulation and secondly, as a local optimisation problem, modifying our basic optimisation algorithm.</p>

scholarly journals Research on the module of color image sonar system based on imx6ull

2021 ◽  
Vol 2005 (1) ◽  
pp. 012052
Author(s):  
Xiaofeng Zhao ◽  
Jing Wang ◽  
Wei Li ◽  
Zhiyuan Wang ◽  
Qijiang Zhang
Keyword(s):  
Color Image ◽  
Sonar System

Lake‐bottom recognition using a wideband sonar system and time‐frequency analysis

1995 ◽  
Vol 98 (1) ◽  
pp. 552-559 ◽  
Author(s):  
Nicolas Andrieux ◽  
Philippe Delachartre ◽  
Didier Vray ◽  
Gérard Gimenez ◽  
Albin Dziedzic
Keyword(s):  
Frequency Analysis ◽  
Time Frequency Analysis ◽  
Time Frequency ◽  
Sonar System ◽  
Lake Bottom
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