• Phonetics and Speech Sciences
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• v.7 no.2
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• pp.157-162
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• 2015

This study reports on the effective way of displaying dynamic formant information on F1-F2 space. Conventional ways of F1-F2 space (different name of vowel triangle or vowel rectangle) have been used for investigating vowel characteristics of a speaker or a language based on statistics of the F1 and F2 values, which were computed by spectral envelope search method. Those methods were dealing mainly with the static information of the formants, not the changes of the formant values (i.e. dynamic information). So a better way of investigating dynamic informations from the formant values of speech signal is suggested so that more convenient and detailed investigation of the dynamic changes can be achieved on F1-F2 space. Suggested method used visualization of static and dynamic information in overlapped way to be able to observe the change of the formant information easily. Finally some examples of the implemented display on some cases of the continuous vowels are shown to prove the usefulness of suggested method.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.6
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• pp.558-563
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• 2008

Optical axis misalignment, which represents the position deviation of the objective lens from the optical axis, is an inevitable assembly error in an optical pick-up. Since the laser power intensity varies with respect to the distance from the optical axis, the misalignment leads to variation of the laser spot power intensity, which is one of the critical factors increasing data bit-error-rate in optical disc drives. In this paper, an auto-adjustment scheme for optical axis alignment is proposed to eliminate the undesirable variation of the laser spot power intensity in optical disc drives. An envelope of the data RF signal is extracted and utilized to detect the optical axis misalignment. Then an adjustment input is added to the driving input of the tracking actuator to shift the objective lens to the optical axis. Finally, the feasibility is verified by experiments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.4
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• pp.503-512
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• 2001

A new adaptation algorithm for the digital predistorter is presented. The proposed technique employs the real-time transmitted signals through HPA for the table update. Hence the proposed algorithm does not depend on modulation format and the signal transmission of HPA is not affected during the adaptation process. The experimental results are presented to verify the proposed method and we obtained about 8.4 dB of ACPR improvement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.7
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• pp.1074-1084
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• 1999

In this paper the bit error probability of noncoherent M-ary FSK system is derived from the probability density function of the envelope of the received signal over a frequency-nonselective slowly m-distributed Nakagami fading channel. Also, the performance of coherent M-ray FSK system is theoretically analyzed, using union bound over the similar fading channel. Then we compare uncoded performance results for M-ary FSK and DPSK signals in Nakagami fading channel.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2262-2264
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• 2003

본 논문에서는 도선의 결함 유무와 결함 위치를 측정하는 방법으로 널리 사용되고 있는 시간 영역 반사파 처리 기법(Time Domain Reflectometry : TDR)의 성능 향상을 위하여 가우시안 형태를 가지는 입력 신호와 상호 상관 관계 함수를 이용한 신호 처리 방법을 제안한다. 일반적으로 TDR은 입력 신호와 반사 신호의 시간 지연을 측정해서 결함 위치를 측정하게 되므로, TDR 방법으로 결함 위치를 측정하는데 있어 시간축 분해능의 정도에 따라 측정 방법의 성능이 크게 좌우된다. 따라서, 본 논문에서는 제한된 시간축 분해능에서 결함 위치 측정의 정확도를 향상시키기 위해 가우시안 형태를 갖는 입력 신호 및 반사 신호와의 상호 상관관계 함수를 사용한다. 한편, 실제 도선에 적용하여 기존의 TDR 방법과 측정 성능을 비교 분석함으로써 본 논문에서 제안하는 방법의 우수성을 검증한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.1-6
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• 2011

In this paper, an 1.5Gbit/s wireless data transmission system using the carrier frequency of 300 GHz band was implemented. The RF front-end was composed of schottky diode sub-harmonic mixer, frequency tripler, and horn antennas for transmitter and receiver, respectively. The LO frequencies of sub-harmonic mixer are 150GHz for transmit chain and 156GHz for receive chain. The ASK(Amplitude Shift Keying) modulation was used in the transmitter and the envelope detection method was used in the heterodyne receiver. The conversion loss of sub-harmonic mixer and implementation system loss were measured to be 9.8dB and 1.2dB, respectively. The 1.5Gbit/s video signal with HD-SDI format was transmitted over wireless distance of 40cm without optical lens(4.2m with optical lens) and displayed on HDTV at the transmitted average output power of $20{\mu}W$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.970-976
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• 2007

This paper presents a novel polar transmitter architecture with a 2-bit sigma-delta modulator. In the proposed architecture, the 2-bit sigma-delta modulator is introduced to suppress quantization noise of conventional sigma-delta modulator. The power amplifier configuration is also modified in a binary form to accommodate the 2-bit digitized envelope signal. The Ptolemy simulation results of the proposed structure show that the spectral property is greatly improved in full transmit band of EDGE system. The fine quantization scheme of the 2-bit modulator lowers the noise level by 10dB without increasing the over-sampling ratio, which may be obtained if the over-sampling ratio increases twofold. Dynamic range is also enhanced up to 5dB owing to the new form of the power amplifier in the transmitter.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.110-117
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• 2016

Passive sonar systems detect and classify the target by analyzing the radiated noises from vessels. If multiple noise sources exist within the sonar detection range, it gets difficult to classify each noise source because mixture of noise sources are observed. To overcome this problem, a beamforming technique is used to separate noise sources spatially though it has various limitations. In this paper, we propose a new method that uses a FDICA (Frequency Domain Independent Component Analysis) to separate noise sources from the mixture. For experiments, each noise source signal was synthesized by considering the features such as machinery tonal components and propeller tonal components. And the results of before and after separation were compared by using LOFAR (Low Frequency Analysis and Recording), DEMON (Detection Envelope Modulation On Noise) analysis.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.5
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• pp.529-536
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• 2019

In this paper, the signals of the sensor for extracting characteristic parameters of the rotor are collected and the performance of the extraction technique is analyzed. To this end, a vibration test league was developed for conducting model tests to analyze the signal characteristics under normal operation. As a result, it is judged that no change in the measured the raw data amplitude will occur in the acceleration sensor with the unbalanced mass measured from the acceleration sensor. Performing FFT showed a significant increase in amplitude of the rotational frequency of 20 Hz as the unbalanced mass increased. The analysis results according to the change in the unequal mass of the speed sensor also showed a significant increase in the 1X Harmonics component, such as the acceleration sensor. There was no change in the amplitude of the acceleration sensor data when the misalignment occurred, and for the Envelope data, the amplitude of 2X (40 Hz) was increased depending on the degree of misalignment. The velocity sensor at change of misalignment also showed similar results to the acceleration sensor, and the peak was reduced at 600 Hz as the load increased in the frequency spectrum.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.1
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• pp.53-60
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• 2017

Most of present ultrasonic distance measurement technologies are based on the measurement of the TOF (: Time of Flight), the elapsed time during which the ultrasonic wave travels from its transmitter to receiver, to evaluate the distance the wave travels during that time. In this case, high distance measurement accuracy requires an accurate measurement of TOF. In order to acquire an accurate TOF, this paper proposes a method that produces the TOF by using a mathematical model of the received signal obtained from a mathematical model of ultrasonic transducer. The proposed method estimates the arrival time of the received signal retrospectively by comparing its wave form obtained after triggering point with its mathematical model in the sense of least-square. Experimental result shows that the effect of variation of triggering point can be decreased by implementing the proposed method.