• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.1023-1028
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• 2012

A MMIC (Monolithic Microwave Integrated Circuit) mixer chip using the Schottky diode of an GaAs p-HEMT process has been developed for the I/Q demodulator of non-contact near field microwave probing system. A single balanced mixer type is adopted to achieve simple structure of the I/Q demodulator. A quadrature hybrid coupler and a quarter wavelength transmission line for 180 degree hybrid are realized with lumped elements of MIM capacitor and spiral inductor to reduce the mixer chip size. According to the on-wafer measurement, this MMIC mixer covers RF and LO frequencies of 1650MHz to 2050MHz with flat conversion loss. The MMIC mixer with miniature size of $2.5mm{\times}1.7mm$ demonstrates conversion loss below 12dB for both variations of RF and LO frequencies, LO-to-IF isolation above 43dB and RF-to-IF isolation above 23dB, respectively.

• Journal of the Korean Magnetics Society
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• v.8 no.4
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• pp.241-248
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• 1998

In accordance with tendency to miniaturization and high frequency operation of electronic products, extensive efforts of miniaturizing magnetic devices such as inductors, transformers and magnetic sensors are being made. In order to study on fabrication and characteristic of micro-magnetic devices, we carried out two sets of experiments. One is to develop a magnetic film that is suitable for high frequency operation, and the other is to develop the fabrication processes for realizing the micro-coil with meander shape. Magnetic films were composed of FeTa(N,C) fabricated by DC magnetron sputtering system. Their microstructures were nanocrystalline structure and magnetic properties showed Bs:13~17 kG, Hc:0.1~0.2 Oe and $\mu$':2000~4000. Cu coil pattern fabricated by selective electroplating process showed good electrical conductivity. In the case of air core inductors, inductance (L) of 50 nH, resonance frequency $(f_R)$ of 700 MHz, and quality factor (Q) of 30 at 200 MHz could be obtained. In the case of close type magnetic inductors, inductance (L) of 150 nH, resonance frequency $(f_R)$ of 100 MHz, and quality factor (Q) of 4 at 10~30 MHz could be obtained.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.3 no.2
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• pp.39-45
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• 2010

In this paper, an equally spaced $3{\times}2$ microstrip patch array antenna based on the fundamental infinite wavelength supported by the composite right/left-handed (CRLH) transmission line (TL) is proposed. The proposed CRLH TL unit cell consists of an inter-digit capacitor to realize left-handed (LH) series capacitance and non-symmetric shunt meander line with a shorted via to realize LH shunt inductance. At the infinite wavelength frequency of 2.09 GHz a 6-port series power divider consisting of a 19 unit cells shows a maximum magnitude difference of 0.73 dB and a $0.52^{\circ}$ maximum phase difference between output ports. The measured resonant frequency and maximum gain of the fabricated array antenna is 2.09 GHz and 10.98 dBi, respectively.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.36T no.3
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• pp.56-63
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• 1999

In this paper, we realize the active PFC(Power Factor Correction) system of BF (Boost Forward) converter with PWM-PFM control technique to control DC output voltage, and to control the input current with sinusoidal wave synchronized by the converter and inverter using power switching element, FET and IGBT. The control circuit of the suggested Boost converter is implemented with a microprocessor 80C196. After making the ratio of output voltage to current as 50V/1A and the duty ratio greater than 0.5. When input voltage is 30V and boost inductance is 1.1mH. We control the voltage changing rate according to the variation of load resistance using a PWM-PFM control technique. And finally we prove experimentally. PF can be improved up to 0.96 using the current shaping technique.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.2
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• pp.157-163
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• 2014

This paper proposes a two-stage step-down buck and a tapped-inductor boost cascaded converter for high efficiency photovoltaic micro-inverter applications. The proposed inverter is a new structure to inject a rectified sinusoidal current into a low-frequency switching inverter for single-phase grid with unity power factor. To build a rectified-waveform of the output current. the converter employs both of a high efficiency step-up and a step-down converter in cascade. In step-down mode, tapped inductor(TI) boost converter stops and the buck converter operates alone. In boost mode, the TI converter operates with the halt of buck operation. The converter provides a rectified current to low frequency inverter, then the inverter converts the current into a unity power-factor sinusoidal waveform. By applying a TI, the converter can decrease the turn-on ratios of the main switch in TI boost converter even with an extreme step-up operation. The performance validation of the proposed design is confirmed by an experimental results of a 120W hardware prototype.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1996.11a
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• pp.291-294
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• 1996

We present the experimental results of high quality factor (Q) inductors fabricated on high-resistivity silicon wafer using standard CMOS process without any modificatons such as thick gold layer or multilayer interconnection. This demonstrates the possibility of building high Q inductors using lower cost technologies, compared with previous results using complicated process. The comparative analysis is carried out to find the optimized inductor shape for the maximum performance by varying the thickness of metal and number of turns with rectangular shape.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.1
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• pp.71-79
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• 1990

An analog phase shifter is designed at the operating frequency 10GHz that is coupled with a hybrid ring and the network connecting an inductor series with a varactor to extend a continuous chage in the phase of the reflected output wave to be produced from a variation in the terminated varactor reactance as a variation in the reverse bias voltage. It is manufactured in a microstripline in consideration of an effect of the dispersion characteristics and discontinuities. As a resuls of an experiment, a change in the phase is achieved over 180 degree from $52.34^{\circ}$ degrees to $235.01^{\circ}$degrees, the transmission loss is -3.6~-14.3dB, and the return loss is -16~-8dB(1.37

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.4
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• pp.1797-1805
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• 2012

In this paper, Power LED(Light Emitting Diodes) is studied to driver as a new lighting system in the spotlight, replacing a large existing lighting system with fluorescent and incandescent lighting. To take advantage a variety of DC power as the boost DC-DC converter design specifications through the inductor L and capacitor C through PSPICE to calculate the best estimate of the value. Converter's switching frequency is 50[kHz], the first Duty Rate was made to increase gradually depending on the value of the detection were, 10[%] in the output voltage. As a result, the simulated Boost Power LED driver characteristics is in comparison with the design specifications, 5[%] or less as the error was approximated. So, when input 15[V] were offered, a stable output 24[V] were obtained, and Dimming Control through the adjustment of brightness and current consumption were obtained to possible result.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.214-222
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• 2008

The equivalent circuit for the RLH-TL is proposed considering radiation effects due to the inclusion of a series capacitor and shunt inductor in a unit cell for the right/left-handed transmission line(RLH-TL). The design equations to realize a specific phase shift at a given frequency is also provided. The S-parameters for unit cells with N=1, 3, 5, and 10 are analyzed in various aspects based on the EM and circuit simulations especially for the purpose of controlling radiation along RLH-TL's. A modification formula for the radiation rate per unit cell is also proposed for good agreement between the EM and circuit simulation results.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.2
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• pp.47-54
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• 1990

In this paper, we design the 4-bit phase shifter which have $22.5^{\circ},45^{\circ},90^{\circ}$ and $180^{\circ}$ phase shift by applying the loaded line and switched network phase shifter. Its phase shift is variable with changing of the stub and passive device parameters. The experiments show the 6.5 dB average insertion loss and $10^{\circ}$ average phase error at center frequency, 6GHz. The results of experiment agree well with the theories except $180^{\circ}$ phase shifter.