• The Journal of the Acoustical Society of Korea
• /
• v.37 no.4
• /
• pp.188-195
• /
• 2018

A new directional linear array structure and its signal processing method are presented to resolve the left/right ambiguity inherent in a linear array. The array structure combines an ordinary acoustic sensor array with a DIFAR (Directional Frequency Analysis and Recording) sensor array, keeping a linear array configuration and gaining a instantaneous left/right discrimination. It presents better PSRR (Port-Starboard Rejection Ratio) in low frequency band and low SNR (Signal to Noise Ratio) situation as compared with a conventional twin linear array, and good compromise to easily upgrade an existing linear array system to a new one with a left/right discrimination capability.

• The Journal of the Acoustical Society of Korea
• /
• v.35 no.5
• /
• pp.403-409
• /
• 2016

Traditional towed line arrays using omni-directional sensor suffer from the well known port-starboard ambiguity, because the direction of arrival is determined by conic angle. The operational method and structure of the sensor arrays method have been proposed to solve this problem. Recently, a lot of research relating to the acoustic vector sensor are studied. In this paper, we study port-starboard discrimination for roll of acoustic vector sensor array. With one omni-directional sensor and three orthogonally-placed directional sensors, an acoustic vector sensor is able to measure both the acoustic pressure and the three directional velocities at the point of the sensor. The wrong axis due to the roll at directional sensors can degrade performance of beamforming. We investigate port-starboard discrimination for roll of sensor array and confirm the validity of performance of beamforming with compensated the roll.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.10
• /
• pp.1116-1120
• /
• 2010

Low cost patch array antenna for high sensitivity electromagnetic(EM) sensor is presented. The operating frequency band of the antenna is 24.05~24.25 GHz. Array structure is the symmetrical pattern by Chebyshev polynomial and the feed point is located in the middle of the array. Also, the gain of the array antenna can be increased by the side wings which are connected with the ground plane. It is proved through simulation and the measurement results that the operating frequency and the side-lobe level(SLL) are rarely changed when the inclined angle of the side wings is varied.

• The Journal of the Acoustical Society of Korea
• /
• v.20 no.7
• /
• pp.31-36
• /
• 2001

Passive sonar system forms the various beams in any desired directions to obtain the improvement in Signal-to-Noise (S/N) ratio, bearing detection and localization of targets, and the attenuation of interferences from other directions. The improvement of beamforming is very important to detect modern underwater targets as noise reduction technology leads to considerably low-level acoustic emissions in the long range in complex environmental sea. In this paper, we proposed the spatial cross correlation beamforming (SCCBF) algorithm using cross correlation matrix of individual hydrophone pairs of linear array sensors. By the theoretical analysis and simulation, the proposed SCCBF is demonstrated that its performances compared to conventional beamforming (CBF) output can be obtain above 3dB of array gain and about half of beam width represented the bearing accuracy in target detection. Also, this paper presents sea test result of linear passive sonar system that the proposed algorithm implemented.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.377-380
• /
• 2000

도플러 로그용 센서를 이용하여 선박의 속도를 측정하면, 선박의 수평방향 이외의 움직임, 즉 핏칭이나 롤링 등에 의한 측정 속도의 부정확성이 문제가 된다. 본 연구에서는 이러한 핏칭과, 수중이라는 환경요인에 기인하여 다른 속도 측정용 센서들이 가지는 문제점을 극복할 수 있도록 진동판을 수평축에서 일정한 각을 가지도록 두 개 또는 네 개를 등 간격으로 배열한 야누스형 초음파 트랜스듀서를 개발하였다. 트랜스듀서 개발을 위하여 그 작동 구조를 해석하고 그에 따라 시제품을 제작한 후, 실험적인 성능 평가를 수행하였다. 시제작된 초음파 트랜스듀서는 지향성 및 감도가 우수하고, 대역폭이 넓은 성능을 가지고 있어, 실제 선박에 장착되어 도플러 로그용 초음파 트랜스듀서로 사용될 수 있는 가능성이 확인되었다.

• Journal of IKEEE
• /
• v.24 no.2
• /
• pp.536-542
• /
• 2020

This paper presents a nature-inspired wideband sprout-leaf shaped antenna with end-fire radiation pattern. A sprout-leaf shape angled-radiator was designed for wide beamwidth radiation patterns for motion detection sensors. An extended and truncated ground plane was used as a reflector for end-fire radiation patterns. To feed the balanced radiator, a broadband microstrip (MS) to coplanar stripline (CPS) balun was utilized with excellent amplitude and phase balance. The proposed antenna demonstrates wide frequency bandwidth from 8.5 to 14.5 GHz with wide beamwidth and the radiation efficiency of 90%. The measured gain is from 4 to 5 dBi and front-to-back ratio was 10 to 20 dB. It has been shown that the proposed antenna can be used for imaging sensors, phased array systems, and radars that require a wide bandwidth and a directional radiation pattern.

• The Journal of the Acoustical Society of Korea
• /
• v.34 no.3
• /
• pp.200-209
• /
• 2015

An underwater sound surveillance system detects and tracks enemy ships in real-time using hydrophone arrays, in which seabed-mounted sensor arrays play a pivotal role. In this paper the conceptual design of seabed-mounted, cylindrical hydrophone arrays for use in shallow coastal waters is performed via finite element calculations. To stabilize the receiving characteristics under the ocean ambient noise, a technique for whitening the ambient noise spectrum using a metal baffle is proposed. Optimization of the array configuration is performed to achieve the directivity in the vertical and azimuthal directions. And the effects of the sonar dome shape and material on the structural vibration and sound scattering properties are studied. It is demonstrated that a robust hydrophone array, having a sensitivity deviation less than 4 dB over the frequency range of interest, can be obtained through the whitening of the ambient noise, the optimization of the array configuration, and the design of acoustically transparent sonar domes.

• Proceedings of the Acoustical Society of Korea Conference
• /
• spring
• /
• pp.177-180
• /
• 2000

소나 시스템에서는 신호 대 잡음비의 향상, 표적의 방위탐지 및 위치 데이터 산출, 간섭신호 제거 등을 위하여 지향성 빔을 만들어 사용한다. 본 논문에서는 선형으로 배열된 센서에서 각 센서쌍들에 대한 상호상관 행렬을 이용한 SCCBF(Spatial Cross Correlation Beamformer) 알고리즘을 제안하였다 이상적인 조건하에서 제안된 SCCBF는 CBF(Conventional Beamformer)에 비해 3dB의 Array Gain을 갖는 것을 이론적으로 검증하고 표적의 탐지 방위정확도를 나타내는 빔폭(Beam Width)이 CBF 보다 0.5배정도가 됨을 검증하고 모의실험을 통하여 이를 입증하였다.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.19 no.9
• /
• pp.922-927
• /
• 2009

The transducers used in active sonar on surface ships are packed in a specific geometry in the array drum in order to meet the requirements such as the source level, directional beam pattern, etc. This paper describes the acoustic characteristics of the cylindrical array which is based on a 64 vertical staves arrangement, each stave composed 5 independent transducers. Firstly, the single transducer on the rigid baffle in the water is analyzed with the Finite Element Method. From the result of the FE analysis nodal velocities on the radiation surface is calculated and used with the boundary conditions of the transducers mounted on the array drum. Then the acoustic pressure is calculated in the field points using the Boundary Element Method and the other acoustic informations, the source level, beam pattern, near field and far-field distance, were acquired.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.54 no.3
• /
• pp.78-86
• /
• 2017

In this paper, we propose hidden object detection system using parametric array based on acoustic signal that is harmless to human body. A transmit signal of the proposed detection system uses a high directive chirp signal generated from parametric array phenomenon, which uses technique to improve a signal to noise (SNR) of a received signal and a distance resolution trough the dechirp processing. The transmit sensor array is constructed as $8{\times}2$ and has a horizontal beam width of $7^{\circ}$ and vertical beam width of $26^{\circ}$. To verify the detection and visualization of the proposed system, a 2-axis driving control system based on linear stage was constructed, and A-scan, B-scan, and C-scan experiments was addressed for hidden object. From experimental results, we detected and visualized the hidden bronze plate and pipe by cloth and the visualized shapes was confirmed. Especially, the obtained errors was $0.015m^2$ for bronze plate, and $0.046m^2$ for pipe.