• Proceedings of the Korean Society of Computer Information Conference
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• 한국컴퓨터정보학회 2019년도 제60차 하계학술대회논문집 27권2호
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• pp.161-162
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• 2019

본 논문에서는 변압기의 이상 신호 데이터를 원거리에서 축적하기 위한 이상 신호 진단 시스템을 제안한다. 이 시스템은 원격으로 변압기의 이상 신호를 수집하여 변압기의 이상을 알아낼 수 있다. 이 시스템은 상용된 통신 모듈의 느린 통신 속도를 고려하여 이상 신호를 RMS-DC 값으로 변환하는 작업을 추가하였다.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제23권2호
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• pp.165-172
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• 2019

Using two or more coaxial lines, if one port is connected in series and the other port is connected in parallel, it can be implemented the wideband transmission line transformer(TLT). Because the wideband TLT utilizes the outer conductor of the coaxial line, it is difficult to predict the characteristics. In this paper, based on the analysis for the transfer characteristic(S21) according to the loss of the each line in ${\lambda}/4$-microstrip line TLT, the operating characteristic of the fabricated wideband 4:1 TLT using two $25{\Omega}$-coaxial lines is investigated. The fabricated wideband TLT shows the notch characteristic in which the transfer signal sharply decreases at ${\lambda}/4$ frequency of the coaxial line and has a value within -0.2dB of the transfer characteristic(S21) in $0.06{\sim}0.2{\lambda}$ frequency range of the coaxial line. This transfer characteristics(S21) can change the operating frequency range slightly and set the optimum transfer characteristic(S21) at the desired frequency by changing the length of the microstrip line.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제18권1호
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• pp.15-23
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• 2007

A simple six-port direct conversion QPSK receiver which is made up of a six-port phase correlator, a signal power detector, and I/Q channel signal de-modulator is designed and implemented in this paper. The output phase signals of six-port phase correlator are also analysed. On the basis of $90^{\circ}C$ phase relation among the six-port phase correlator output signals, the QPSK de-modulation circuit is designed by a simple circuit. The six-port phase correlator is made up of $90^{\circ}$ hybrid branch line and power detector. The six-port phase correlator, which is designed in frequency range of 11.7 to 12.0 GHz, gets the phase error characteristics less than $5^{\circ}$. By considering matching network and amplitude balance in the designed fiequency range, the designed six-port direct conversion QPSK receiver demodulates the I and Q signals with performance less than $5^{\circ}$ phase error.

• Journal of IKEEE
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• 제13권1호
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• pp.77-86
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• 2009

A wavelet Electrocardiogram(ECG) detector and its analog-to-digital converter(ADC) for low-power implantable cardiac pacemakers are presented in this paper. The proposed wavelet-based ECG detector consists of a wavelet decomposer with wavelet filter banks, a QRS complex detector of hypothesis testing with wavelet-demodulated ECG signals, and a noise detector with zero-crossing points. To achieve high-detection performance with low-power consumption, the multi-scaled product algorithm and soft-threshold algorithm are efficiently exploited. To further reduce the power dissipation, a low-power ADC, which is based on a Successive Approximation Register(SAR) architecture with an on/off-time controlled comparator and passive sample and hold, is also presented. Our algorithmic and architectural level approaches are implemented and fabricated in standard $0.35{\mu}m$ CMOS technology. The testchip shows a good detection accuracy of 99.32% and very low-power consumption of $19.02{\mu}W$ with 3-V supply voltage.

• Journal of IKEEE
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• 제8권2호
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• pp.166-171
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• 2004

This paper describes a CMOS time to digital converter (TDC) that measures the interval between two signals and converts to a digital signal. There are various methods to measure the time interval. But several architectures have a limitation in resolution and in conversion time. Moreover, they have complex algorithms. But the proposed TDC circuit has achieved a high resolution (25ps) by using a high-speed digital sampler and simple algorithm. The sampler detects when input signals comes into the TDC and output is coded. The proposed multiphase clock generator was also implemented to achieve 25p resolution.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제16권12호
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• pp.2716-2724
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• 2012

In this paper, a Phase Difference-to-Voltage Converter (PDVC) has been introduced into a conventional fractional-N PLL to suppress fractional spurs. The PDVC controls charge pump current depending on the phase difference of two input signals to phase frequency detector. The charge pump current decreases as the phase difference of two input signals increase. It results in the reduction of fractional spurs in the proposed fractional-N PLL. The proposed fractional-N PLL with PDVC has been designed based on a 1.8V $0.18{\mu}m$ CMOS process and proved by HSPICE simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제8권6호
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• pp.1402-1409
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• 2007

In this paper, we propose various types of AGC algorithms for implementing the OFDM communication systems. For the high-speed packet transmission, in this paper, we assume the OFDM system with relatively long and repeated preambles. We propose the maximum sample value counter for counting the number of maximum sample. In the maximum sample value counter, we use the buffer for the digital signal buffering. Finally, the counting value of the maximum sample value counter controls the gain control signal generator by using gain control table automatically.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제14권5호
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• pp.1071-1077
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• 2010

The six-port phase correlator using lumped elements was designed and fabricated in this paper, also the receiving performance of L-band direct conversion receiver using lumped six-port phase correlator element was analyzed. The proposed L-band lumped six-port phase correlator element was composed of a resistive power divider and the twist-wire coaxial cables. The proposed lumped six-port structure provides the small-sized configuration and wide-band characteristics. The performance of the L-band lumped direct conversion receiver structure was measured under the conditions of 1.69 GHz frequency for LO-CW signal and RF-QPSK signal, which are input signals for the lumped six-port phase correlator element. The direct conversion receiving structure using the proposed lumped six-port phase correlator element can recovered the good digital I/Q signal.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제12권1호
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• pp.33-38
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• 2008

The probability of an oscillation occurrence in M/W frequency conversion repeaters is low on account of the different operating frequency of the input and output signals. The probability of interference caused by the M/W frequency conversion repeaters to other systems is also low because the systems are used in the line-of-sight. Therefore M/W frequency conversion repeaters are generally used for retransmitting the signal received from base station to the islands. This paper describes the design and implementation of analog predistorter for M/W frequency conversion repeaters in mobile communications. The M/W repeaters convert IF frequency of 1010+/-10MHz to RF frequency of 11GHz. A predistorter can be designed for the M/W repeater operating in either IF or M/W frequency. In this paper IF predistorter operated in 1010MHz is designed and implemented because a M/W predistorter operated in 11GHz is difficult to implement. The IF predistorter can linearize RF modules in the repeater followed by IF stages. The performance test results show that the implemented analog predistorter improves ACPR of 10dB at the output power of 25dBm with the signal frequency of 10.805GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제12권7호
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• pp.1180-1186
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• 2008

The LNB phase noise of user terminal for high data rate satellite transmission was analyzed in this paper. The phase noise severely affects the service performance in low data rate transmission as well as multi-mode signal for high data rate. As the satellite link frequency is increased, the effects of phase noise for multi-mode signal is increased. The phase noise of LNB, which is operated in high frequency band, is about equal to the transmission system phase noise and have an major effects on service performance degradation. The available transmission mode was analyzed in presence of phase noise of LNB and analysis method for LNB phase noise spectrum distribution was proposed in multi-mode signal.