• Journal of the Korean Institute of Telematics and Electronics C
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• v.36C no.5
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• pp.48-55
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• 1999

This paper describes automatic gain control circuit (AGC) design techniques for CMOS CCD camera interface systems. The required gain of the AGC in the proposed system is controlled directly by digital bits without conventional extra D/A converters and the signal settling behavior is almost independent of AGC gain variation at video speeds. A capacitor-segment combination technique to obtain large capacitance values considerably improves the effective bandwidth of the AGC based on switched-capacitor techniques. A proposed layout scheme for capacitor implementation shows AGC matching accuracy better than 0.1 %. The outputs from the AGC are transferred to a 10b A/D converter integrated on the same chip. The proposed AGC is implemented as a sub-block of a CCD camera interface system using a 0.5 um n-well CMOS process. The prototype shows the 32-dB AGC dynamic range in 1/8-dB steps with 173 mW at 3 V and 25 MHz.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.3 s.357
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• pp.20-25
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• 2007

The periodic domain-inversion in the selective areas of $Ti:LiNbO_3$ Mach-Zender waveguides was performed and band-pass modulators and single sideband (SSB) modulators were fabricated by using domain-reversal. The domain wall velocity was precisely controlled by real-time analysis of a poling-induced response current under an applied voltage. The domain wall velocity was significantly affected by the crystal orientation of the domain wall propagation which influenced the final domain geometry. In a certain case, the decomposition of $LiNbO_3$ crystal was observed, for example, under the condition of too fast domain wall propagation. The fabricated band-pass modulator with a periodic domain-inversion structure showed the maximum modulation efficiency at 30.3 GHz with 5.1 GHz 3dB-bandwidth, and SSB modulator was measured to show 33 dB USB suppression over LSB at 5.8 GHz RF.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.3
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• pp.51-58
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• 2008

This paper is a study of a prevention of power folding controller's thermal degradation. Power folding technology has been applied for many fields such as side rear vision mirror of vehicles, windshield wiper, antenna, power window. These controllers have been comprised with traditional DC moors, Switching electronic devices, and relays. But this methods have a limitation to overcome such problems of product reliability, endurance, noise margins. Therefore on this paper, to detect the movement of motor, sensing motor brush noise on a load sensing part has been used and controlling a precise RC timing control minimizes the thermal deterioration of motor. And using MOS FETs as a electronic switching device increases life-time and liability of control circuit. After testing such circuit and control method, repetition of operating time, cut-off time, wide operation voltage, power noise margin ware increased over eleven-fold.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.419-426
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• 2002

A new active lossless snubber for half-bridge dual converter(that is called'dual converter') is proposed in this paper It features soft switching(ZVS) as well as turn-off snubbing in both main and auxiliary switches. Therefore, it helps the dual converter to operate at the higher frequency with a higher efficiency and smaller-sized reactive components. Moreover, since it uses parasitic components, such as leakage inductances and switch output capacitances etc, to achieve the ZVS of power switches, it has simpler structure and lower cost of production. The operational principle, theoretical analysis, and design consideration are presented. To confirm the operation, features, and validity of the proposed circuit, experimental results from a 200w, 24V/DC-200V/DC proto-type are presented.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.3
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• pp.747-754
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• 2013

This paper proposed a new transponder detection method to reduce tag recognition time and simplify anti-collision process in RFID systems. In conventional systems, a transponder in detectable area is passively recognized by responding to a reader command. In addition, if there are multiple tags in the area, a collision between tags occurs by responding at the same time to a command and anti-collision process begins. In the proposed method, tags are actively recognized without any command from a reader which results to reducing a tag recognition time and simplifying anti-collision process. To compare transponder recognition time, the process of transponder recognition in conventional systems is analysed. A circuit to detect transponder directly is developed and antenna voltage variation of a reader in the appearance of multiple transponders is analysed for the implementation of the proposed method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.12
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• pp.2508-2519
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• 1994

In this thesis, two possible schemes for power feeding are considered. The first one is the network power feeding, and the other is the power feeding from the rechargeable battery. Though each scheme has its merits and demerits, the domestic network operator has proposed the latter due to the large deviation of line resistance, high power loss, and safety. This scheme, however, has several problems. The usage is limited by the life of battery leading to the failure of minimal voice service for many hours. The space occupation of that battery is another serious problem. Moreover, the network opeator should have overhead of maintenance and repair. In order to alleviate such the difficulties, the sealing current is introduced through the subscriber loop. Flowing the current into the loop prevents from rusting. This thesis designs a power controller using PEB2025 to control various amount, duration, and period of this sealing current, to achieve the optimum current supply for sealing.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.44-53
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• 2008

In this paper, we present the design of delta-sigma modulation-based class-D amplifier for driving headphones in portable audio applications. The presented class-D amplifier generates PWM(pulse width modulation) signals using a single-bit fourth-order high-performance delta-sigma modulator. To achieve a high SNR(signal-to-noise ratio) and ensure system stability, the locations of the modulator loop filter poles and zeros are optimized and thoroughly simulated. The test chip is fabricated using a standard $0.18{\mu}m$ CMOS process. The active area of the chip is $1.6mm^2$. It operates for the signal bandwidth from 20Hz to 20kHz. The measured THD+N(total harmonic distortion plus noise) at the $32{\Omega}$ load terminal is less than 0.03% from a 3V power supply.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.12
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• pp.2618-2624
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• 2009

Harmonics (or distortion in wave form) has always existed in electrical power systems. It is harmless as long as its level is not substantial. However, with the recent rapid advancement of power electronics technology, so-called nonlinear loads, such as variable frequency drives for motor power/speed control, are increasingly finding their way to shipboard or offshore applications. In this paper a new approach to direct torque control (DTC) of induction motor drive is presented. In comparison with the conventional DTC methods the inverter switching frequency is constant and is dramatically increased, requiring neither any increase of the sampling frequency, nor any high frequency dither signal. The well-developed space vector modulation technique is applied to inverter control in the proposed DTC-based induction motor drive system, thereby dramatically reducing the current harmonics. As compared to the existing DTC approach with constant inverter switching frequency, the presented new approach does not invoke any concept of deadbeat control, thereby dramatically reducing the computations.

• Radiation Oncology Journal
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• v.4 no.2
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• pp.173-177
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• 1986

Since March 1985, we have treated cancer patients with local hyperthermia using a 2,450-MHz microwave thermogenerator. Prior to clinical trial, a 2,450-MHz microwave generator remodeled from a household electric range was tested and evaluated to test its clinical applicability. We studied the thermoprofile and tried to find out suitable electric power ranges to produce optimal temperature of $42-44^{\circ}C$ in a lump of meat, agar phantom and animal tumor models. The present study confirmed the intratumoral temperature to be $1-3^{\circ}C$ higher than in surrounding normal tissue.

• Journal of Advanced Navigation Technology
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• v.17 no.3
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• pp.332-345
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• 2013

In this paper, recently, it is described to the piezoelectric transformer technology develops, because it was have to favorable characteristics such as electromagnetic-noise free, compact size, higher efficiency, and superior power density, flux linkage, noiseless, etc. its resonance frequency was used to output waveform of a sine wave. A rotor speed identification method of induction motor based on the theory of flux model reference adaptive system(FMRAS). The estimator execute the rotor speed identification so that the vector control of the induction motor may be achieved. The improved auxiliary variable of the model are introduced to perform accurate rotor speed estimation. The control system is composed of the PI controller for speed control and the current controller using space voltage vector PWM techniuqe and DC-DC converter. High speed calculation and processing for vector control is carried out by digital signal one chip microprocessor. Validity of the proposed control method is verified through simulation and experimental results.