• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.6
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• pp.817-824
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• 2016

A simultaneous bidirectional transceiver over a single wire has been developed in a 65 nm CMOS technology for a command and control bus. The echo signals of the simultaneous bidirectional link are cancelled by controlling the decision level of receiver comparators without power-hungry operational amplifier (op-amp) based circuits. With the clock information embedded in the rising edges of the signals sent from the source side to the sink side, the data is recovered by an open-loop digital circuit with 20 times blind oversampling. The data rate of the simultaneous bidirectional transceiver in each direction is 75 Mbps and therefore the overall signaling bandwidth is 150 Mbps. The measured energy efficiency of the transceiver is 56.7 pJ/b and the bit-error-rate (BER) is less than $10^{-12}$ with $2^7-1$ pseudo-random binary sequence (PRBS) pattern for both signaling directions.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.383-386
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• 2008

We developed a fiber-optic Bragg grating sensor system using a SOA fiber laser for over heat detection in power systems. To compensate the nonlinear wavelength tuning of the fiber laser, we used fixed passband wavelengths from Fabry-Perot ITU filter as reference wavelengths. Gaussian line-fitting algorithm was also used to reduce the FBG peak detection error. Compared with a highest-peak-detection and a polynomial-fitting method, the proposed Gaussian fitting algorithm could drastically reduce the measurement errors. Also the SOA fiber laser made it possible to enhance the signal-to-noise-ratio even with several kilometers of lead fiber.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.327-334
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• 2000

In this paper, the circuit model using circuit averaging method for full bridge for full bridge converter is suggested. This model can represent the physical characteristics of converter circuits appropriately. At most of high capacity DC-DC converter application parts, full bridge converter is adapted for main circuit of power supply. Design and analysis of full bridge converter is no trouble with circuit model. The validity of circuit model is verified through computer simulation and practical welding experiment of welding machine with full bridge converted model.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.319-323
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• 1990

VSS controller is suited for systems where the robust performances in the presence of parameter variations and disturbances are most important. The practical realization of such robust VSS algorithm using DSP ($TMS_{32020}$) is dicussed in this paper. PWH-like control signal which is produced by directly using VSS control algorithm substitutes the PWM amplifier. And the armature current is used in construction of switching function for the purpose of increasing switching frequency. In order to compensate steady state error produced by various external disturbances practical integral compensator is considered.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1998.06a
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• pp.165-170
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• 1998

In this paper, the effect of nonlinear distortion, caused by a high-power amplifier (HPA) in an orthogonal frequency division multiplexing (OFDM) system, on the receiver part is analyzed. Since the HPA, which can be modeled by a memoryless Volterra system, distorts OFDM signals in a nonlinear fashion, the received signal at each subchannel includes the multiplicative distortion of 1-st order as well as additive nonlinear distortion of higher-order. The nonlinear distortion can be viewed as a nonlinear interchannel interference (NICI) since it consists of harmonic distortions and intermodulation distortions, produced by other subchannels affecting the subchannel of interest. In this paper, were analytically derive the variance of NICI in terms of average input power using the Volterra model for HPA, and then calculate the bit-error rate (BER) performance of an OFDM system. Also, we propose a simple method to compensate for the phase distortion in OFDM system amplified by HPA, and calculate its BER performance. Validity of the proposed approach is verified by computer simulations for an OFDM system employing 16-QAM constellation input.

• Journal of KSNVE
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• v.9 no.5
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• pp.1036-1041
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• 1999

This paper aims for the development of the high power sonar system for measuring the velocity of a moving object. The high power sonar system transmits two gated 190 kHz sinusoidal signals with 1.6 [ms] time interval to the moving object. Then the sonar system detects and calculates the changed time delay of the reflected ultrasonic signals in order to derive the velocity of the moving object. The transmission part uses a high power amplifier so that 250 W gated sinusoidal signals can be transmitted to the transmitter. 1M RAM is utilized for transmitting and storing of the ultrasonic signals. The time delay is calculted by the cross-correlation technique between the transmitted signals and the received signals. The measured value from the high power sonar system is compared with directly measured values by photo diodes. The result confirms the adjacency to 0.3% error.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.7
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• pp.3117-3130
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• 2016

High peak-to-average power ratio (PAPR) of transmitted signals is a major drawback in Multicarrier modulation (MCM) systems. Companding transform is a well-known method to reduce the PAPR without restrictions on system parameters such as the number of subcarriers, frame format and constellation type. In this paper, a novel adaptive companding scheme, mainly focuses on compressing the large signals into the desirable distribution, is proposed to reduce the PAPR with low implementation complexity. In addition, formulas to calculate its PAPR and bit error rate (BER) performance are also derived. Simulation results confirm that the proposed scheme can achieve an effective tradeoff between PAPR reduction and BER performance by carefully choosing the companding parameter.

• Proceedings of the KIEE Conference
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• 1994.07b
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• pp.1523-1525
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• 1994

This paper describes a proposed very fast transient overvoltages(VFTO) measurement system suited for established gas insulated switchgear(GIS). The detecting system consists of a shield electrode connected to a buffer amplifier, and the transmission of the detected signal to an oscilloscope is made through an optical fiber. The bandwidth of the measurement system is 5 Hz to 30MHz. When determining the voltage dividing ratio by use of the commercial frequency voltage, the error is less than 0.5 %. Also, the data were obtained by the electric field probe and the high voltage probe, and their deviation for voltage dividing ratio were less than 1 %.

• Journal of KSNVE
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• v.2 no.1
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• pp.49-59
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• 1992

The motion analysis of a translation device driven by a piezoelectric actuator is performed to identify the mechanics of impact drive mechanism and to find the maximum speed waveform. The translation device is modeled as a semidefinite two-degree-of-freedom system. The motion analysis includes effects of friction force between moving mass and contact surface, dynamics of voltage amplifier and piezoelectric elements, and hysteresis of piezoelectric actuator. Base on the model, simulation studies are carried out and then compared with experimental results. It is found that the error between moving distances obtained by analysis and experiment is less than 15% and that the actual motion of moving mass is well predicted by the analytical work, finally, precision positioning experiments are carried out by using a proximity sensor as a feedback sensor. Position control of moving mass is initiated by the maximum speed waveform and finely tuned by the scaled down waveform so that accurate positioning is accomplished within the resolution of the sensor.

• Proceedings of the IEEK Conference
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• summer
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• pp.221-224
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• 2004

This paper proposed an ultra low-power CMOS exponential voltage-mode circuit using the Pseudo-exponential function for realizing the exponential characteristics. The proposed circuit provides high dB-linear output voltage range at low-voltage applications. In a $0.25\;\mu m$ CMOS process, the simulations show more than 35 dB output voltage range and 26 dB with the linearity error less than $\pm0.5\;dB.$ The average current consumption is less than 80 uA. The proposed circuit can be used for the design of an extremely low-power variable gain amplifier (VGA) and automatic gain control (AGC).