• The Journal of the Acoustical Society of Korea
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• v.41 no.5
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• pp.481-491
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• 2022

The active sonar transmission system consists of a transmitter that outputs an electrical signal and an underwater acoustic transducer that converts the amplified electrical signal into an acoustic signal. In general, the transmitter output characteristics are dependent on load impedance, and an underwater acoustic transducer, which is a transmitter load, has a characteristic that the electrical impedance varies largely according to frequency when driven. In such a variable impedance condition, the output of the active sonar transmission system may become unstable. Hence, this paper proposes a design and control technique of a sonar transmitter for transmitting a stable transmission signal even under variable impedance conditions of an underwater acoustic transducer in an active sonar transmission system. The electrical impedance characteristics of the underwater acoustic transducer are experimentally analyzed, and the sonar transmitter is composed of a single-phase full-bridge inverter, an LC filter, and a matching circuit. In this paper, the design and output control method of the sonar transmitter is proposed to protect the transmitter and transducer. It can secure stable output voltage characteristics even if it transmits the Linear Frequency Modulation (LFM) signal. The validity is verified through the simulation and the experiment.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.1
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• pp.33-39
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• 2017

In this paper, an effective feature which is capable of classifying targets among the detections obtained from 2D range-bearing maps generated in active sonar environments is proposed. Most conventional approaches for target classification with the 2D maps have considered magnitude of peak and statistical features of the area surrounding the peak. To improve the classification performance, HOG(Histogram of Gradient) feature, which is popular for their robustness in the image textures analysis is applied. In order to classify the target signal, SVM(Support Vector Machine) method with reduced HOG feature by the PCA(Principal Component Analysis) algorithm is incorporated. The various simulations are conducted with the real clutter signal data and the synthesized target signal data. According to the simulated results, the proposed method considering HOG feature is claimed to be effective when classifying the active sonar target compared to the conventional methods.

• The Journal of the Acoustical Society of Korea
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• v.20 no.2
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• pp.44-51
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• 2001

This Paper the practical echo signal synthesis model to predict the target strength and signal shape of a submarine for a valuable tool to active sonar engineer. It is based on UTAHID (Underwater TArget by Highlight Distribution) model which is relocated highlight points along to external hull for aspect angle, and synthesized echo signal by modified grouping highlights to internal scatter cloud. Proposed model is analyzed target strength characteristics on various incident pulse length, and synthesis signal signature, target time spreading loss, echo elongation effect and so on. Thus it can be efficiently used in various real systems related to underwater target echo signal synthesis, that is, active sonar, acoustic countermeasure and surveillance system.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.3-7
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• 2001

In active sonar system using CW signal, when the noise included reverberation has not the white characteristics, the CFAR detector estimates high threshold. Because of this reason it cannot detect targets and not resolve the closely spaced multiple targets. In order to solve these problems, we propose an adaptive reverberation rejection filter The proposed filter is composed of an adaptive filter and a fixed filter with its coefficients. To study the performance of the proposed adaptive reverberation rejection filter, various experiments have been performed under In moving active sonar environments. As a results, the proposed method has the improved performance than the previous methods.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.75-81
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• 2015

In active sonar system, clutters degrade performance of target detection/tracking and overwhelm sonar operators in ASW (Antisubmarine Warfare). Conventional clutter reduction algorithms using consistency of local peaks are studied in multi-ping data and tracking filter research for active sonar was conducted. However these algorithms cannot classify target and clutters in single ping data. This paper suggests a single ping clutter reduction approach to reduce clutters in mid-frequency active sonar system using echo shape features. The algorithm performance test is conducted using real sea-trial data in heavy clutter density environment. It is confirmed that the number of clutters was reduced by about 80 % over the conventional algorithm while retaining the detection of target.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.10
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• pp.2137-2142
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• 2012

Many studies in detection and classification of the targets in the underwater environments have been conducted for military purposes, as well as for non-military purpose. Due to the complicated characteristics of underwater acoustic signal reflecting multipath environments and spatio-temporal varying characteristics, active sonar target classification technique has been considered as a difficult technique. And it has a difficult in collecting actual underwater data. In this paper, we implemented the simulator to synthesize the active target signal, to extract feature and to classify the target in the underwater environment. In target signal synthesis, highlight and three-dimensional model are used and multi-aspect based hidden markov model is used for target classification.

• The Journal of the Acoustical Society of Korea
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• v.20 no.3
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• pp.91-97
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• 2001

Since the new field information of target signal is important in the development and verification of active sonar system, experimental method and simulation technique are widely used in order to analyze the detail characteristics of target scattered echoes. Therefore, in this paper, the scale target experiment is performed to develope and Improve the target signal simulation model. Since the experimental results show that the specular reflection is the major component among scattering mechanisms, the target signal simulation model based on the Geometric Optics Theory (GOT) is developed. Complex target is separated into simple shapes, known as canonical shape. The contribution from individual canonical shapes are summed with proper phase and amplitude to produce the target strength of the whole complex body. Simulated target signal is compared with the experimental results and discussed.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.38-43
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• 2017

Many studies about generating images of seabed using active sonar have been carried out but image resolution enhancement is still an important problem. Many methods have been proposed to improve sonar resolution and the approach using narrow beam width is commonly and widely applied to enhance azimuth resolution. Unfortunately, this has technical limitations to reduce the beam width. Therefore, signal processing techniques are essential to achieving higher azimuth resolution when an array with conventional beam width is employed. This paper proposes a new approach that utilizes overlapped beams to obtain higher resolution.

• Journal of Ocean Engineering and Technology
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• v.11 no.3
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• pp.163-169
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• 1997

The simulation of target-scattered echo with the moving sonar platform and target in 3-dimensional ocean environment is essential to validate and evaluate the performance of a sonar system. This paper presents the improved target signal simulation on the basis of the highlight(HL) model and its realtime algorithm. In order to simulate the scattering highlight, the highlight is represented as a directional scatterer. The realtime generation algorithm of the target signal is realized by use of DSP chip, TMS320C40, where the 40 channels are equally separated to form a parallel processing task in 4 processors. The presented realtime-version of target signal simulation can be used as a target signal simulator in the development of ACM(Acoustic Counter Measure) and advanced sonar signal processing techniques.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.179-185
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• 2017

The problem that occurred in the design/fabrication/testing of the wideband transmitting power amplifier for an embedded active SONAR (Sound Navigation and Ranging) system operating underwater was analyzed and the solution of the problem was proposed in this paper. Wideband acoustic SONAR systems had been developed in order to improve the underwater detection performance. The underwater acoustic transmission system had been also developed to achieve the wideband SONAR system. In this paper, the wideband acoustic transmission signal was generated using a 2 Level sawtooth type Class D PWM (Pulse Width Modulation) which was not complicated to implement. When the sonar signals having two or more frequencies were simultaneously generated, parasitic frequencies were added to the original signals by integer multiples of the frequency difference of the original signal. To cope with this problem, we proposed a way to remove the parasitic frequency from the source signal through modeling and simulation of the implemented power amplifier and PWM control hardware using MATLAB and Simulink.