• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.05a
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• pp.656-659
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• 2017

In this paper, we propose a digital method for transmitting audio signals using LED visible light communication system. In the proposed method, we compare the method for transmitting audio signal in analog signal and the method for transmitting by digital signal. When amplifying the audio sound and transmitting the analog signal using the LED visible light communication, attenuation corresponding to the transmission distance occurs, and there is a disadvantage that it is noisy. In order to overcome this, we propose a method for transmitting digital audio signals. The proposed method has the advantage of reducing the influence of noise, but it turned out that it is affected much by the LED blinking speed. Various methods to overcome this need to be continuously studied.

• Journal of the Korean Society for Railway
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• v.12 no.2
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• pp.249-253
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• 2009

This paper dealt with the insulation evaluation by a measurement of partial discharge(PD) on traction motors used in a hybrid vehicle. The PD method has been accepted as an effective and a non-destructive. technique to evaluate insulation performance of low-voltage electric and electronic devices. In this paper, the PD measurement system which was manufactured with a coupling network, a low noise amplifier, and an associated electronics is described. The PD measurement system has the frequency bandwidth of $1[MHz]{\sim}30[MHz]$ at -3 [dB] and the stable sensitivity of 19 [mV/pC] for the traction motor. From the experimental results, discharge inception voltage (DIV) and apparent charge (q) were $1,100[V_{rms}]$ and 105 [pC] for the used motor, and $1,400[V_{rms}]$ and 84 [pC] for the new one. By comparing the DIV and q, we could evaluate the insulation condition for the traction motors.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.487-495
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• 2022

This paper describes the design and development of a high-power transmit receive module(TRM) for mounting on X-band synthetic aperture radar(SAR) of the NEXTSat-2. The TRM generates a high-power pulse signal with a bandwidth of 100 MHz in the target frequency range of X-band and amplifies a low-noise on the received signal. Tx. path of the TRM has output signal level of more than 200 watts (53.01 dB), pulse droop of 0.35 dB, signal strength change of 0.04 dB during transmission signal output, and phase change of 1.7 ˚. Rx. path has noise figure of 3.99 dB and gain of 37.38 ~ 37.46 dB. It was confirmed the TRM satisfies all requirements. The TRM mounted on the NEXTSat-2 flight model(FM) which will be launched using the KSLV-II (Nuri).

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.5
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• pp.11-17
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• 2003

It is well known that the double integration of measured acceleration records is one of the most difficult signal processing, particularly in the measurements on civil engineering structures, The measured accelerations of civil engineering structures are usually non-stationary and contain non-gaussian low-frequency noises, which can be significant causes of numerical instabilities in double Integration, For the de-noising of this kind of signals, wavelet transform can be very effective because of its inherent processing features for non-stationary signals, In this paper, the de-noising algorithm for the double integration is proposed using the modified wavelet transform, which is extended version of ordinary wavelet transform to process non-gaussian and low-frequency noises, using the median filter concept, The example studies show that the integration can be improved by the proposed method.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.176-181
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• 2006

We have built the close range Dicke type radiometer with 35GHz of frequency, which consists of two stage low noise amplifier and diode detector to calibrate temperatures of materials. We have present thermal calibration methods using millimeter-wave radiometer. Output voltages linearly increase with temperatures between 299K and 309K. We are able to measure lower temperature using the liquid nitrogen although results are somewhat unstable.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1918-1919
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• 2011

상체 지원 외골격 로봇은 크게 인간의 근력을 보조하는 형태와 인간의 근력을 증강하는 형태가 있다. 여기서는 인간의 근력을 증강하는 외골격 로봇을 중심으로 기술하고자 한다. 이러한 외골격 로봇은 팔의 EMG (Electromyograph;근전도) 신호를 측정하는 방법보다는 손의 힘을 직접 감지하는 방법을 통한 팔꿈치와 어깨의 엑추에이터를 구동하는 방식을 취하는 경향이 있다. 본 논문에서도 후자의 방식을 이용하여 손에 작용하는 힘을 분석하여 외골격 로봇을 움직이는 방식을 취하였다. 손의 힘 중에서도 인간을 중심으로 볼 때 위방향과 전진방향의 힘을 분석하기 위하여 2개의 F/T(Force/Torque) 센서를 사용하였으며 팔을 벌리는 동작은 엑추에이터 없이 자유롭게 동작이 가능하도록 설계하였다. 이러한 위방향 및 전진방향 힘의 크기를 팔꿈치와 어깨의 엑추에이터의 동작으로 바꾸어 인간의 동작을 도울 수 있고 힘을 증폭할 수 있는 외골격 로봇을 설계 제작하였다. F/T 센서는 손의 힘을 전기적 신호로 바꾸어주는 로드셀로 이루어지며 손의 힘을 최대한 잘 반영하기 위한 구조를 고안하였다. F/T 센서의 전기신호는 증폭기를 거쳐서 잡음을 제거한 후에 A/D 변환하여 processor에서 처리되어진다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.48 no.5
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• pp.10-15
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• 2011

Histogram equalization is an effective method to enhance the contrast of the image. However, it can result in unwanted artifacts such as excessive contrast enhancement and noise amplification. These artifacts can be reduced by modifying an intensity mapping function which is generated by histogram equalization. In this paper, we present a variational approach to the modification of the intensity mapping function. We define a functional whose minimization produces a modified intensity mapping function. Experimental results show that the intensity mapping function obtained by the proposed method can enhance the contrast of the image without visual artifacts.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.71-74
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• 2012

We have manufactured a close range Dicke type radiometer which consists of two stage low noise amplifier and diode detector. Frequency range of this system is 35 GHz. And this is used for studying temperature calibration on specific objects. We have present millimeter-wave radiometer's thermal calibration method and its characteristics. From absolute temperature 299K to 309K, in proportion to increase temperature, output voltages are linearly increased. In this case, undefined objects can be measured thermal noise temperature relatively. Overall from absolute temperature 214K to 309K, we have obtained relation of temperature and output voltage;V= 0.03601K - 10.70517.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1C
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• pp.1-7
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• 2011

Recently, multi-hop relay transmission has drawn much attention owing to its advantage of coverage extension at low power consumption. In this paper, we derive a performance bound of multi-hop communication systems with multiple amplify-and-forward relays when the optimal path is selected. The bound is derived in generalized Nakagami fading channels with different parameters for each hop by applying the geometric mean bound to the path signal-to-noise ratio (SNR) and obtaining the moment generation function of the bound. It is shown that the bound based on the geometric mean is closer to the actual performance of optimal path selection when the fading effect is small.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.1020-1027
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• 2005

In this paper, economic miniature RF transmitter module for intelligent transportation system(ITS) is described. This module which consists of ASK modulator, frequency synthesizer, power amplifier is operating at 5.8 GHz frequency band and implemented by using LTCC process technique. Thus, ultra small size of 0.8 CC and improved electrical performances has been obtained. From the test results, transmitting characteristics of 10 dBm ouput power and -46 dBc interchannel interference with 1.024 Mbps ASK modulated have been shown. Frequency synthesizer as a transmitting signal source reveals very short locking time of 26 usec and outstanding phase noise of -115 dBc/Hz at 1 MHz offset from 5.8 GHz center frequency.