• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1633-1640
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• 2016

In this paper, we propose a open-ended rectangular microstirp patch antenna with fork-shaped feeding structure. This antenna extends the effective bandwidth by transforming single or multi resonant frequency and is designed planar monopole structure with microstrip line to satisfy the WLAN bands (2.4 - 2.484, 5.15 - 5.35, 5.25-5.825 GHz). The substrate is printed in 0.8 mm thickness on an FR-4 board. A commercial 3D simulation tool was used to analyze surface current and electromagnetic field distribution in order to analyze the operation mode and reconfiguration principle of antenna. According to the lengths of individual patches, simulated reflection loss was compared to obtain optimized values. When it was designed with the optimized values, it satisfied WLAN bands (2.380 - 2.710, 4.900 - 5.950 GHz), if the switch is off, and 2.4 WLAN band (2.380 - 2.710 GHz). From the fabricated and measured results, measured results of return loss, gain and radiation patterns characteristics displayed for operating bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.9 s.100
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• pp.949-956
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• 2005

In this paper, a new CPW-fed cross shape fractal antenna having a self-affinity is presented. This novel configuration, which has anisotropic scaling symmetry, makes smaller profile characteristic compared to the fractal antenna using a self-similarity. Increase of the iteration coefficient, which leads to decrease of the fundamental resonant frequency, shows a good impedance matching condition and multi-band characteristics due to new surface current paths. The radiation patterns are similar to those of monopole antennas. In the K3 stage of iteration, the proposed antenna shows a measured maximum gain 2.27 dBi at 940 MHz. A commercially available software based on the FDTD algorithm has been used to obtain the predicted results. In addition, an RT/Duroid 5880 substrate has been employed for the experimental results.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.4
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• pp.188-193
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• 2017

In this paper, a ZVS-PWM high-frequency inverter with a PWM control function is applied to commercial system 220[Vrms], and a resonator type ZVS-PWM high-frequency inverter circuit with a fixed-two methods were proposed. The parameters of the transformer model equivalent circuit of a copier fixing device, which is an essential element in the parameter optimization of the proposed circuit, are obtained by using a high-frequency amplifier and its frequency characteristics are described. The proposed method compared to the existing single-ended ZVS-PFM high frequency inverter can suppress the voltage and current peak value of the power semiconductor switching device and reduce the switching loss. The efficiency of the proposed method itself is 98[%] at rated power output. Also, the efficiency of 96[%] can be obtained even at low output, so that the proposed high frequency inverter is very efficient inverter. The total efficiency from the commercial AC input to the inverter output is 93[%] at rated, which is considered efficient for use in copying machines. In addition, the diode bridge loss accounts for the largest portion of the overall system efficiency distribution. On the other hand, the nonparallel filter has a very low loss.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.35-43
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• 2007

In this paper, the inductive power collector using electromagnetic induction for vehicle such as the PRT(Personal Rapid Transit) system is suggested and son ideas for power collector design to improve tile power transfer performance are presented. And also, the analysis of the inductive power transfer system in conjunction with series resonant converter operating variable high frequency is shown. Of particular interest is the sensitivity of the complete system to variations in operational frequency and parameters. In inductive power transfer system electrical power is transferred from a primary winding in the form of a coil or tract to one or more isolated pick-up coils that my relative to the primary. The ability to transmit power without contact enables high reliability and easy maintenance that allows inductive power transfer system to be implemented in hostile environments. This technology has found application in many fields such as electric vehicles, PRT(Personal Rapid Transit) etc. But, low output power is generated due to a loosely coupled characteristic of the large air-gap. Therefore, we will show you various characteristic of inductive power transfer system as double layer construction of secondary winding, which was divided in half to increase both output current and output voltage, a model of power collector and parallel winding structure, a model of concentration/ decentralization winding and the effects of parameter and operational frequency variation.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.481-483
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• 2008

본 논문은 다양한 종류의 전원을 구비해야 하는 다중출력 전원 시스템을 위한 영전류 스위칭 LLC 공진형 Post-regulator를 제안한다. 기존의 LLC 공진형 컨버터는 정밀한 다중 출력을 얻기 위해 추가의 DC/DC 컨버터가 구성되었고, 이는 전력 변환 효율 감소 및 제조 원가 상승의 단점을 갖고 있다. 제안된 컨버터는 각 소자의 내압 및 전류 스트레스가 작고, 요구되는 출력 당 1 개의 보조 스위치만으로 구현되므로 저가격화에 유리하다. 또한 전력이 전달되는 시점의 공진 전류의 초기값을 가변함으로서 정밀하게 제어되는 다중 출력 전압을 획득할 수 있고, 각 전압의 출력 순서 제어도 가능한 장점이 있다. 뿐만 아니라, 독립된 공진탱크를 이용하기 때문에 공진탱크 설계가 용이하며, 최근 전자 제품의 추세인 슬림화의 요구에 부응할 수 있다. 또한, 제안된 Post-regulator의 모든 전력 스위치는 ZCS가 가능하므로 스위칭 손실을 최소화 할 수 있다. 최종적으로 본 논문에서 제안한 영전류 스위칭 LLC 공진형 Post-regulator를 제작하고, 고찰된 실험결과를 제시하여 제안된 컨버터 및 전원시스템의 우수성과 이론적 분석의 타당성을 검증한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.12
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• pp.941-947
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• 2017

This paper reports a fractional-N phase-locked-loop(PLL) frequency synthesizer that is implemented in a $0.35-{\mu}m$ standard CMOS process and generates a quadrature signal for an FRS terminal. The synthesizer consists of a voltage-controlled oscillator(VCO), a charge pump(CP), loop filter(LF), a phase frequency detector(PFD), and a frequency divider. The VCO has been designed with an LC resonant circuit to provide better phase noise and power characteristics, and the CP is designed to be able to adjust the pumping current according to the PFD output. The frequency divider has been designed by a 16-divider pre-scaler and fractional-N divider based on the third delta-sigma modulator($3^{rd}$ DSM). The LF is a third-order RC filter. The measured results show that the proposed device has a dynamic frequency range of 460~510 MHz and -3.86 dBm radio-frequency output power. The phase noise of the output signal is -94.8 dBc/Hz, and the lock-in time is $300{\mu}s$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.9
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• pp.1037-1044
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• 2008

Radiation efficiency and antenna gain, in this paper, can be increased by the slot on EMI shield painted on the mobile phone back cover. When the EMI slot which has proper dimension and location is located on the EMI paining area in the phone, the increment of antenna current density due to mutual coupling between the antenna and slot derives increment of antenna efficiency. For the verification of EMI slot effect, we apply the EMI slot to the mobile phone which is operating on GSM/DCS/USPCS/WCDMA quad band, and measure $S_{11}$ and antenna efficiency. It's shown that resonant frequency is not changed and radiation efficiencies to frequency channels by EMI slot are increased from 0.21 % to 8.96 %.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.5
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• pp.223-228
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• 2018

In this paper the water sensor using a coaxial cavity resonator is designed and manufactured. The water sensor which can sense water drop linearly has been constructed with voltage controlled oscillator(VCO), coaxial cavity resonator, RF switch, RF detector, A/D converter, DAC and micro controller. The operating frequency range of the designed water sensor is from 2.5GHz to 3.2GHz and the input voltage and current source are 24[V/DC] and 1[A]. The designed sensor circuit includes VCO, RF switch, RF detector which varies the frequency characteristics of the devices in the high frequency of 3GHz. And so we should correct the error of the frequency characteristics of those devices in the sensor circuit. To do this, we make the reference path which switches the signals to the RF detector directly without sending it to the resonator. According to the result of simulation and measurement, we can see that there is 0-50MHz difference between simulated resonator frequency and manufactured resonator frequency.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.5
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• pp.819-827
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• 1997

In this paper, a new modeling of a fine actuator for an optical pick-up has been proposed and multiobjective optimization of the actuator has been performed. The fine actuator is constituted of the bobbin which is supported by wire suspension, the coils which wind around the bobbin, and the magnets which cause the magnetic flux. If current flows in the coils, magnetic force is so produced as to be balanced with spring force of wire, so the bobbin is pisitioned. In this model the transfer function from input voltage to output displacementof bobbin has been obtained so that we can describe this integrated system with electromagnetic and mechanical parts. Wire suspension is regarded as a continuous Euler beam, damper as distributed viscous damping, and bobbin as a rigid body which can move up- and down- ward motion only. According to the model, the high frequency dynamic characteristics of the fine actuator can be known and the effect of damping can be investigated while the conventional second order model cannot. In multiobjective optimization, two objective functions have been chosen to maximize the fundamental frequency and the sensitivity with respect to the input voltage of the actuator so that Pareto's optimal solutions have been obtained using .epsilon.-constraint method. These objective functions will satisfy the trends which will enhance the access speed and reduce the tracking error in the optical pick-up technology of next generation. In the result of optimization, we obtain the designs of the optical pick-up fine actuator which has high speed, high sensitivity and low resonant peak. Furthermore, we offer the relation between two object functions so that the designer can make easy choice.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.1-7
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• 2010

This paper presents empirical equations indicating the high frequency performance characteristics of air-cored induction coil sensors with their constructional parameters. An air-cored induction coil sensor is widely used due to good linearity at low frequency ranges but the sensor has weakness of relatively low sensitivity to the magnetic field. At high frequency ranges, the sensitivity can be dramatically increased, largely depending on the frequency of the injected field, and this property can be a great asset to some electromagnetic inspections, since they utilize the interrogating current with a fixed frequency. The application of this property of the coil sensor requires the estimation of its high frequency performance. We made experiments on the frequency responses of the coil sensors under diverse constructional conditions and, on the basis of the experimental results, the high frequency performance, such as the resonant frequency and the sensitivity at the frequency, was estimated, as a function of the constructional parameters of the coil sensor. The good agreements between experimental and estimated data were reported.