• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.1 s.116
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• pp.24-30
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• 2007

A windmill-shaped loop antenna is designed for polarization diversity. Its circumference is almost 10 times that of a conventional small loop antenna whose circumference is less than ${\lambda}/10$ but its the radiation pattern is omni-directional. An identical parasitic element is placed over the radiator to match the antenna input impedance. An equivalent transmission line and RLC circuit models are shown to fully describe for the windmill-shaped loop antenna. The proposed antenna has a bandwidth of 6 % with input VSWR less than 2:1 and a polarization purity of 15 dB at 2.6 GHz, and the gain of 1.5 dBi. The simulated and measured results show fairly good agreement.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.10
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• pp.941-944
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• 2016

This paper proposes 24 GHz power amplifier for automotive collision avoidance and surveillance short range radar using Samsung 65-nm CMOS process. The proposed circuit has a 2-stage differential power amplifier which includes common source structure and transformer for single to differential conversion, impedance matching, and power combining. The measurement results show 15.5 dB maximum voltage gain and 3.6 GHz 3 dB bandwidth. The measured maximum output power is 13.1 dBm, input $P1_{dB}$ is -4.72 dBm, output $P1_{dB}$ is 9.78 dBm, and maximum power efficiency is 17.7 %. The power amplifier consumes 74 mW DC power from 1.2 V supply voltage.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.11
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• pp.1311-1316
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• 2014

To be used in a transmitter of a satellite transponder of this paper, X band 25W power amplifier module, a part constituting of high-power amplifier is transmitted to the equipment for transmitting to geostationary communications satellites(36,000Km distance). PAM consisted a total of four power amplifier module has a high output characteristic of the high-output amplifier is used in the ground station. Used in conjunction with the structured type power amplifier module is composed of Serial Combining Structure. This PAM(Power Amplifier Module) configured by combining the circuit with the power amplifier, 10 MMIC chips and the Al2O3 thin film substrate using a Hybrid Technique of power amplifier module, was implemented at X band PAM(Power Amplifier Module) of 25W grade.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.143-151
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• 2018

In this paper, a novel hybrid configuration combining a phase-shift full-bridge (PSFB) and a half-bridge resonant LLC converter is proposed for the On-Board Charger of Electric Vehicles (EVs). In the proposed converter, the PSFB converter shares the lagging-leg switches with half-bridge resonant converter to achieve the wide ZVS range for the switches and to improve the efficiency. The output voltage is modulated by the effective-duty-cycle of the PSFB converter. The proposed converter employs an active reset circuit composed of an active switch and a diode for the transformer which makes it possible to achieve zero circulating current and the soft switching characteristic of the primary switches and rectifier diodes regardless of the load, thereby making the converter highly efficient and eliminating the reverse recovery problem of the diodes. In addition an optimal power sharing strategy is proposed to meet the specification of the charger and to optimize the efficiency of the converter. The operation principle the proposed converter and design considerations for high efficiency are presented. A 6.6 kW prototype converter is fabricated and tested to evaluate its performance at different conditions. The peak efficiency achieved with the proposed converter is 97.7%.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.219-226
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• 2000

In this paper, we design and implement a IF(intermediate frequency) module for WLL(wireless local loop) CDMA(code division multiple access) basestation. The implemented IF transceiver is consists of transmitter, receiver and local oscillator. The considered signal bandwidth is 10 MHz and the local carrier frequency is 40 MHz. As test results, the If transmitter output power is -5dBm $\pm3dB$when the baseband input is -10dBm $\pm3dB$, and the IF receiver output power is -10dBm $\pm3dB$when the IF input is -5dBm $\pm3dB$. Also the AGC(automatic gain control) circuit has dynamic range of 9 dB from -7dBm to +2dBm with output power 2dBm. And the group delay characteristic is analyzed by comparing the phase delay from 1 MHz to 5 MHz and the phase distortion is very low. We can conclude that this IF system can be applied to high speed data rate communication system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.134-141
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• 2007

This paper presents a frequency synthesizer(FS) for 5.2GHz/2.4GHz dual band wireless applications which is designed in a standard $0.18{\mu}m$ CMOS1P6M process. The 2.4GHz frequency is obtained from the 5.2GHz output frequency of Voltage Controlled Oscillator (VCO) by using the Switched Capacitor (SC) and the divider-by-2. Power dissipations of the proposed FS and VCO are 25mW and 3.6mW, respectively. The tuning range of VCO is 700MHz and the locking time is $4{\mu}s$. The simulated phase noise of PLL is -101.36dBc/Hz at 200kHz offset frequency from 5.0GHz with SCA circuit on.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.478-487
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• 2003

In this paper, a type and special feature of Multi-level inverter used in medium-voltage and high-capacity motor driver is introduced. Especially, a power quality and structural advantages of H-Bridge Multi-level inverter is described. It presented the specific structure of power circuit, design method, controller composition and PWM techniques of the cascaded H-Bridge Multi-level inverter which is developed. The feasibility of the developed product based on 3,300V lMVA 7-level H-bridge inverter was studied by experiments and we get conclusion that 1)generate of near-sinusoidal output voltage; 2)is low dv/dt at output voltage; 3)reduce the harmonic injection at input; Experiment demonstrate that it is very economical in productivity because of using the existing production technique and examination equipment, and has the reliability and a good maintenance due to the structure of Power Cell unit combination as well as low cost IGBT.

• Journal of Sensor Science and Technology
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• v.14 no.2
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• pp.78-84
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• 2005

A contactless recharging device for totally implantable middle ear systems has been designed as a pillow type that the user can recharge the implanted battery with taking a rest. The proposed device uses the electromagnetic coupling between the transmitting coil and the receiving coil. To supply sufficient power for the implanted circuits, each coil uses LC resonance and the implanted device uses voltage doubler. A power MOSFET is used for switching the DC voltage of LC parallel circuit and the switching frequency demands on a programmable frequency generator which is controlled by microcontroller. In order to improve the electromagnetic coupling efficiency at specific positions of coil which may vary with the displacement of head, the optimal location of receiving coil was studied, and the 5 transmitting coils in a pillow for recharging the implant module was designed. From such a recharging experiment, it was found that the proposed device could provide the sufficient operating voltage within the distance of 4 cm between pillow and the implanted device.

• Journal of Sensor Science and Technology
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• v.20 no.4
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• pp.272-278
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• 2011

Recently, the performance of binaural hearing aids is rapidly improved with the technology advancement of wireless communication, digital signal processing, and integrated circuit design. However, the previous hearing aids developer platforms can't be applied to binaural hearing aids developing, because it has no consideration for wireless communication and binaural hearing control. Also, the previous developer platforms are not easy to use for the algorithm development, because programming languages are limited. In this paper, we designed and implemented the open platform board for binaural hearing aids developing. The designed board can be programmed by general programming language and can be used wireless communication module. In order to verify the designed open platform board, we used the volume control algorithm using two open platform board. As a result of experiment, we verified the performance of designed and implemented open platform board that was successfully operated the binaural hearing control and the wireless communication.

• Journal of Sensor Science and Technology
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• v.13 no.1
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• pp.12-19
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• 2004

The tinnitus which is the one of the auditory disease is a phenomenon that the patients feel the sound in the ear or the head when there is no sound sources. There have been many therapies for this tinnitus so far, but it is known that the TRT (Tinnitus Retraining Therapy) is the most effective therapy. So we designed and developed the controllable white noise generator for TRT. It must be designed as small as possible for user's convenience, such as the ITE (In The Ear) type hearing aids. It used the thermal noise as the white noise source. And filter and tone control circuits are used at the end of the noise generation part to control the white noise characteristics. This link of the controllable circuits is used to change the white noise's characteristic for the various tinnitus patients' characteristic. we can confirm that the designed and implemented controllable white noise generator which is a ITE type operates properly by the experiments of filter and tone control circuit.