• The Journal of the Acoustical Society of Korea
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• v.15 no.6
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• pp.110-116
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• 1996

In this paper a novel method improving the accuracy of DTMF tone reception in ARS system is proposed. ARS system should allow users to generate DTMF signals while it is sending voice guidance. It is not unocmmon, in this case, that a portion of transmitting voice signals cross-talks to the receiving channel and it often results in interfering with the receiving DTMF signals. Serious degradations including DTMF tone missing, false alarm and so forth have been introduced for the above reason. To overcome this phenomena, we have proposed a way eliminating the frequency spectra representing DTMF signals bands from the transmitting voice signal by using notch filters. This method also employs bandpass filters of which the frequency responses are reciprocal to those of the notch filters incorporated with the DTMF receiver. It is shown that a drastic improvement has been achieved with respect to the DTMF tone detection with little deterioration of voice guidance quality.

• The Journal of the Acoustical Society of Korea
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• v.41 no.1
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• pp.16-29
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• 2022

This paper presents a Doppler shift estimation method and signal processing schemes for Direct Sequence Spread Spectrum (DSSS) transmission to overcome the Doppler shift due to the moving of the underwater communication unit. The proposed method estimates a Doppler shift via 2 step procedures using the preamble with the two 64-length Frank sequences which has a good self-correlation characteristic and is insensitive to the Doppler shift. Furthermore, a packet of DSSS underwater mobile communication and a RAKE receiver are designed using the proposed Doppler shift estimation method. Due to the modulation scheme of the designed DSSS underwater mobile communication using Differential-Quadrature Phase Shift Keying (DQPSK) for the data symbol transmission, the RAKE receiver dose not need a phase tracking and easily makes coherent signals among the combining RAKE branches. The designed RAKE receiving scheme including the proposed Doppler shift estimation method successfully decides information data using the DSSS signal transmitted from the pseudo-moving transmitter with velocity upto about 17.5 m/s.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.1
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• pp.99-106
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• 2017

Audible Pedestrian Signal(APS) is an additional equipment to provide information about pedestrian signals in non-visual formats such as audible tones and verbal messages. It can provide information to pedestrians about the location and directions of a crosswalk, and the traffic signal status. In general, a pedestrian who is visually impaired uses a 358.5MHz wireless remote controller to activate the APS and crosses at the crosswalk with the help of the APS. The existing APS can only receive an activation message from the remote controller. Therefore, the APS has an issue, especially at intersections, that all APSs within the communication range of the remote controller are activated simultaneously. It makes to confuse the visual impaired pedestrians. In this paper, we propose a BLE-enabled APS that can enable two-way communication via Bluetooth with a smartphone. The proposed system solves the problem and provides them with additional information, so that visually impaired pedestrians can cross at the crosswalk more conveniently.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.363-364
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• 2004

본 연구에서는, 초음파 단층 화상 장치의 구현을 목적으로, 횡 진동모드의 초음파 트랜스듀서를 원통 내부 벽면에 배열하고 송신부와 수신부를 선택적으로 구동하는 방식의 진단용 초음파 토모그래피의 데이터 송수신부를 제작하였다. 제작된 원통형 트랜스듀서 어레이의 평가를 위해, 각 소자의 주파수특성을 확인하였다. 또한, 원통형 트랜스듀서 어레이의 구동부의 각 진동소자에 적절한 지연시간을 부여하여 음장을 측정한 결과, 양호한 합성평면파가 방사됨을 확인할 수 있었다.

• The Journal of the Acoustical Society of Korea
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• v.35 no.3
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• pp.175-182
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• 2016

For application to several MHz photoacoustic imaging systems, a needle hydrophone was designed and fabricated by using PMN-PZT piezoelectric single crystal, and its characteristics were evaluated through comparison with a commercial PVDF(Polybinylidene Fluoride) hydrophone of which receiving sensitivity is known. The simulation using the KLM model results show that the peak receiving impulse response for $50{\Omega}$ terminating impedance of the fabricated hydrophone is -261.6 dB re $1V/{\mu}Pa$ and the frequency response is relatively flat over 2 ~ 12 MHz with fluctuation less than 5 dB. The measurement results using tone burst signals also show that it has higher (ave. 10.9 dB) sensitivity than the commercial hydrophone in 2 ~ 8 MHz, and the receiving sensitivity of $-255.8{\pm}2.8$ dB re $1V/{\mu}Pa$ was measured for the fabricated hydrophone. In addition, it is known that the photoacoustic signals and the image of a hair obtained by a mechanical scanned photoacoustic imaging system with the fabricated hydrophone were bigger and better than those obtained with the commercial hydrophone.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.191-196
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• 2016

A development on the indoor positioning technologies and services has been proceeded very actively. Among the several positioning technologies, the TDOA(Time Difference of Arrival) technology using acoustic signal has the best positioning performance. Because so many people use their own smartphones, the location of the smartphone is important, and the TDOA technology should be employed to use the acoustic signal for the positioning. For the digital signal processing with the acoustic signal, the signal should be sampled, and as the sampling rate increases, the positioning accuracy could be improved instead of processing time burden. In this paper, the position estimation error according to the sampling rate is analyzed, and the appropriate sampling rate for the positioning system is proposed.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.155-161
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• 2015

As the popularity of the smartphone becomes increase, indoor smartphone positioning technology has been actively studied. The acoustic signal generated from the smartphone is received from the several microphones at the relative positioning system, and the trigger signal is proposed to mitigate the multipath effect and the effect is verified. But for the simple trigger method, there would be error occurred according to the variation of the distance or surrounding noise. In this paper, in order to resolve the problems, the dynamic trigger threshold technology is proposed and its effect is verified by the experiment.

• Journal of the Korea Convergence Society
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• v.9 no.4
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• pp.143-150
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• 2018

This work conducted the experimental analysis on ultrasonic acoustic matching in order to measure the accuracy of gaseous fuel level values. The experimental devices were used as 12V-DC supply, control T1 board, oscilloscope (DS01072B), ultrasonic probe and pattern table. The research models were designed by ceramic assay which can determine the transmitting and receiving energies. The result of the ringing area could verify the increased characteristics in the order of D (0.180m) < E (0.184m) < B (0.204m) < A (0.234m) < F (0.244m) < C (0.247m) models based on initial 2.9V of the maximum peak voltage. From the experimental results, the model designed by Ø21*3+2t of the matching layer was notable in that the most outstanding directivity energy could be created.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.3
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• pp.317-327
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• 2021

Low Frequency Active Sonobuoy(hereinafter referred to as LFAS) are being developed in Korea in consideration of compatibility with existing overseas sonobuoys, and a communication device for acoustic signals receiving and operating control of LFAS has been developed. The communication device needs to verify compatibility with the existing Sonobuoy, and for this purpose, the standardized Sonobuoy communication protocol was applied. The communication device is designed/manufactured to transmit the acoustic signal received in real time from the Sonobuoy through VHF band RF communication to the data processing device, and transmit CFS/CSG commands for operation control to the Sonobuoy through UHF band RF communication. In order to verify the manufactured communication device, the communication status and performance were verified by interlocking test through Ultra Electronics' PASS-II equipment and domestically developed electronic device of Sonobuoy. In addition, operability was verified through environmental tests, water tanks, and marine operations. In the future, the communication device of sonobuoy can be used for verification of the Sonobuoy developed in Korea.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.1
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• pp.1-12
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• 1997

The acousto-optical spectrometer as a new type backend of the receiver system for radio astronomical observations is manufactured for radio signal analysis. We studied on the effect of Acousto-Optic and Acousto-Optic devices and designed the optics system. We manufactured the optical mount and the CCD detector for deflected beam and interface card. This acousto-optical spectrometer consisted of a laser, optics, acousto-optic deflector, CCD detector and Interface card. This system use He-Ne laser as a light source and use optics to get parallel beam and to focus the deflected beam. Acousto-optic deflector converts IF signal to ultrasonic wave and deflect the laser beam according to the Bragg deflection. The ultra wide band acousto-optic deflector has 1 GHz bandwidth and a total of 2,048 channel Charge Coupled Device for signal detection. In this study, we discuss the theoretical description on the effect of Acousto-optics, the design of the optics, manufacture of optical mount, CCD detector, interface card and we presented the results of experiment. As a result of measurement, we have 1,000 channels bandwidth from CCD channels.