• The Journal of the Acoustical Society of Korea
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• v.22 no.4
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• pp.276-285
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• 2003

In this paper, we present real-time implementation of a R2MFC/DTMF (R2 Multi Frequency Combinations/Dual Tone Multiple Frequency) tone receiver/sender using a high performance DSP (Digital Signal Processor) and apply it to a carrier class VoIP (Voice over Internet Protocol) gateway system. The Receiver utilizes the Goertzel filter and the sender adopts the harmonic resonant filter. We describe, in detail, the techniques of multi-channel real-time implementation on a Texas Instruments TMS320C62x DSP such as effective PCM (Pulse Code Modulation) in/out by means of DMA (Direct Memory Access) and McBSP (Multi Channel Buffered Serial Port) and message communication via HPI (Host Port Interface), etc. From experimental results, we confirmed that the optimized code provided 780 channel capacity at 250㎒ C6202, and the our R2MFC/DTMF receiver/sender met ITU-T (International Telecommunication Union-Telecommunication) specifications.

• KSCI Review
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• v.2 no.1
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• pp.55-67
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• 1995

Recently, it is possible to high speed transmission of the non-voiced data, including voice, data, moving image instead of voice only in the past by changing the communication method to digital form from analog owing to the development of semiconductor and computer technology which for information transmission of the remote point. By doing so, we can get the improvement of the noise effect and low cost but the loss of transmission bandwidth. It is necessary to take some method in oreder to reducing the fading which is propotional to transmission bandwidth during the transmission of radio communication channel, especially. When we design the digital communication system, we must considered to the fading effect in order to determination of the transmitting power, modulation /demodulation method, transmission speed, bit error rate. This paper mainly concerns to the method to the channel simulator which descrives the fading effect during the transmission by computer model and digital filter modeling of the radio fading channel by unsing the transmitting and received signal. By taking the inverse of the characteristic of the modeled filter, it is possible to improvement of the communication system by reducing the distortion and inter-symbol interference which occurs in the channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.603-614
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• 2005

In this paper, digital ultra-narrowband Walky-Talky using direct conversion method for CQPSK modulation scheme is implemented with satisfying the requirements of APCO P25. RF transceiver design and implementation scheme that minimize the influence of DC-offset and AC-coupling at ultra-narrowband is proposed. This scheme also minimizes the influence of nonlinear characteristic at power amplifier fir CQPSK modulation method. Test results of full system including DSP module and direct conversion RF transceiver show that FCC emission mask at 36.8 dBm PEP meets the standard requirements. The characteristic of receiver AGC by PWM control signal is linear at 40 dB dynamic range and voice communication at input power level of -116 dBm is successful. Also it is verified that the performance of BER versus frequency offset and versus SNR meets the standard requirements.

• Journal of the Korean Society of Physical Medicine
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• v.14 no.1
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• pp.121-129
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• 2019

PURPOSE: This study was conducted to measure the effects of cervical stabilization exercises on neck pain, forward head posture, and the acoustic characteristics frequency and amplitude modulation of patients with chronic neck pain caused by forward head posture using pressure biofeedback. METHODS: 20 patients with chronic neck pain and voice disorders presenting at the S Exercise Center in Daegu, Korea, were included in the study. A cervical stabilization exercise program of 50 minutes per session was performed three times a week for eight weeks. Pressure biofeedback was utilized to determine the impact of the exercises on neck pain, forward head posture, and the acoustic characteristics of the patients. The measurements were taken prior to and after the intervention to determine any changes. RESULTS: A significant improvement in neck pain, craniovertebral angle and the acoustic characteristics frequency and amplitude modulation of the patients was demonstrated after the intervention (p<.05). CONCLUSION: Cervical stabilization exercises were demonstrated to have a significantly positive effect on neck pain, forward head posture, and vocalization stability in patients with chronic neck pain in the current study based on measurements taken using a pressure biofeedback system. This indicates that an improvement in forward head posture positively impacts postural stability and vocalization. Future studies investigating a greater range of interventions designed to improve neck pain and acoustical effects in patients with chronic neck pain and forward head posture patients are warranted.

• The Journal of the Acoustical Society of Korea
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• v.28 no.5
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• pp.432-440
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• 2009

Recently, the necessity of underwater acoustic communication and demand for transmitting and receiving various data such as voice or high resolution image data are increasing as well. The performance of underwater acoustic communication system is influenced by underwater channel characteristic. Especially, a delay spread caused by reverberation and multi-path induces the ISI (Inter-Symbol-Interference) and reduces the communication performance. In this paper, we study the OFDM (Orthogonal Frequency Division Multiplexing) technique for robust the delay spread in underwater channel. We also use the clipping method to overcome the performance degradation in high PAPR (Peak-to-Average Power Ratio). We confirm the performances of underwater communication system by the underwater channel model simulation model and experiment in small water tank. As a result, the multi-carrier modulation with clipping method presented low BER and the previous single carrier modulation had high BER.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.167-172
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• 2006

In this paper, the 25W power amplifier for UHF band radio transceiver has been designed and realized. The power amplifier was composed of drive, power amplifier and control stages. Feedback topology and coaxial line baluns were used for wide band operation. The VDMOS, which has reliable performance for linearity and efficiency, was used for power device and designed to operate as push-pull amplification at Class AB Bias. The power amplifier designed in such a way was found to show stable AM modulation performance when voice signal was detected at the gate stage, with being designed and realized to meet output specifications of commercial air traffic control transmitter.

• Journal of Advanced Navigation Technology
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• v.9 no.2
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• pp.121-130
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• 2005

In this paper, we designed and fabricated the VHF wireless transmitter for air traffic control. Fundamental performance of the investigated wireless transmitter is designed and fabricated to satisfy existing commercial wireless transmitter specification for air traffic control. 25 W and 50 W of output power can be generated by changing the power amplification part only. It is based on transmitting voice communication using AM modulation. Investigated wireless transmitter for air traffic control consists of four module parts: power supply, control, low power transmission and power amplification. We designed 1W transmitter to operate without power amplification part. It can be used properly in a basic component of CNS/ATM.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.1
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• pp.97-104
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• 1999

In this study we show a telemedicine system using a DSP, which gives fast and exact medical data such as the ECG signal of the external emergency patient and enables the patient to get temporary treatments under the direction of a doctor in the hospital. This transceiver, which is able to treat the real time transmission of dynamic medical data captured by the measuring instrument and bidirectional communication of voice signal, is implemented using DSB-SC as modulation and demodulation technique and digital filter of each terminal are implemented as FIR filter. The system designed with DSP in this study is very small and compact and it can k, furthermore, to support additional biomedical signals just by renewing the software.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.78-81
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• 2009

한의학에서 신장(腎臟)은 단순히 소변을 만들어내는 곳으로 보는 것이 아니라 정력과 생식 활동을 담당하는 곳으로 표현하고 있다. 이러한 신장은 두 개의 강낭콩처럼 생긴 모양을 띄고 있으며 서로 마주 보고 있고 등에 붙어 있어 체내의 조절 기능을 수행하고 있다. 이와 같은 역할을 수행하는 신장에 이상이 발생하면 신부전, 신장염, 신우염 및 부종 등의 신장 질환을 앓게 된다. 따라서 본 논문에서는 신장 기능의 이상 유무를 손쉽게 판단하기 위한 방법으로 음성 분석을 통한 자가 진단법을 제안하고자 한다. 이를 위해 한의학에서 제시하고 있는 신장 질환자에 대한 목소리 패턴을 객관적 지표로 설계하기 위해 정상인과 신장 질환자를 대상으로 음성의 고저(高低)에 해당하는 분석 요소를 적용하여 피실험자 집단간의 비교, 분석을 실험으로 입증하고자 한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.3
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• pp.635-642
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• 2000

We have been derived theoretically the SER's and CLP's of Wireless ATM (WATM) cells employing an OFDM/16QAM modulation scheme in wireless channel modeled as a frequency selective Rayleigh fading channel. The amount of the performance improvement of WATM- OFDM/16QAM systems adopting various coding techniques has been evaluated. In frequency selective Rayleigh fading channel, considering CLP : $10^{-3}$ as a criterion, it is observed that the performance improvement of about 14 dB is obtained in terms of $E_b/N_o$ by employing an OFDM scheme. It is also confirmed that convolutional coding technique gives better performance than the other coding techniques. Especially, when the convolutional codes are adopted to WATM-OFDM/16QAM systems, voice transmission services are sufficiently available with 5 dB of $E_b/N_o$.