• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.12-16
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• 2018

In this work, a voltage controlled oscillator (VCO) monolithic microwave integrated circuit (MMIC) was demonstrated for 10-GHz band motion detecting sensors. The VCO MMIC was fabricated using a $2-{\mu}m$ InGap/GaAs HBT process, and the tuning of the oscillation frequency is achieved by changing the internal capacitance in the HBT, instead of using extra varactor diodes. The implemented VCO MMIC has a micro size of $500{\mu}m{\times}500{\mu}m$, and demonstrates the value of inserting the VCO into a single chip transceiver. The experimental results showed that the frequency tuning characteristic was above 30 MHz, with the excellent output flatness characteristic of ${\pm}0.2dBm$ over the tuning bandwidth. And, the VCO MMIC exhibited a phase noise characteristic of -92.64 dBc/Hz and -118.28 dBc/Hz at the 100 kHz and 1 MHz offset frequencies from the carrier, respectively. The measured values were consistent with the design values, and exhibited good performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.74-77
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• 2000

A pulsed Nd:YAG laser has been used in a wide variety of fields : measuring, material processing and so on. In a material processing, it is very important to control the laser energy density. A pulse repetition rate and a pulse width are regarded as the most dominant factors to control the energy density of laser beam. In this study, pulsed Nd:YAG laser system was designed and manufactured to control the laser output usefully and easily. This system adopted the sequential charge and discharge circuit is controlled by 80196 micro- processor. As a result, it is found that laser output is controlled minutely by changing laser input and pulse repetition rate, and usefully by using 80196 microprocessor.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.279-282
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• 2005

A real-time measurement and control system was developed, This system is used for nurses at hospitals to check the residual quantity and changing time of Ringer's solution in nurses' room. Load Cell is utilized as a sensor to check the residual quantity of Ringer's solution, This Load Cell detects the physical changes of Ringer's solution and transfers electronic signal to the amplifier. Amplified analog signal is converted into digital signal by NO converter. Developed Embedded system, which computes these data with microprocess(8052) then makes it possible to monitor the residual quantity of Ringer's solution real-time on a server computer. A Checking system on Residual Quantity of Ringer's Solution Using Load cell cut costs using a simple design for a circuit

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.4
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• pp.267-272
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• 2010

In this paper, a Gm-C LPF utilizing common-mode feedforward (CMFF) CMOS inverter type operational transconductance amplifier (OTA) has been designed and verified by circuit simulations. The CMFF CMOS inverter OTA was optimized for wide input linearity and low current consumption using a standard 0.18 ${\mu}m$ CMOS process; gm of 100 ${\mu}S$ and current of 100 ${\mu}A$ at supplied voltage of 1.3 V. Using this optimized CMFF CMOS inverter type OTA, an elliptic 5th order Gm-C LPF for GPS specifications was designed. Gain and frequency tuning of the LPF was done by changing the internal supply voltages. The designed Gm-C LPF gave pass-band ripple of 1.6 dB, stop-band attenuation of 60.8 dB, current consumption of 0.60 mA at supply voltage of 1.2 V. The gain and frequency characteristics of designed Gm-C LPF was unchanged even though the input common-mode voltage is varied.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.73-80
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• 2020

The 3D printing of electronics has been a major application topics in additive manufacturing technology for a decade. In this paper, wireless power transfer (WPT) technology for 3D electronics is studied to supply electric power to its inner circuit. The principle of WPT is that electric power is induced at the recipient antenna coil under an alternating magnetic field. Importantly, the efficiency of WPT does rely on the design of the antenna coil shape. In 3D printed electronics, a flat antenna that can be placed on the printed plane within a layer of a 3D printed part is used, but provided a different antenna response compared to that of a conventional PCB antenna for NFC. This paper investigates the WPT response characteristics of a WPT antenna for 3D printed electronics associated with changes in its design elements. The effects of changing the antenna curvature and the gap between the wires were analyzed through experimental tests.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.63-71
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• 2016

Installed PV module in field is affected by shading caused by various field environmental factors. Bypass diodes are installed in PV module for preventing a power loss and degradation of PV module by shading. But, Bypass diode is easily damaged by surge voltage and has often initial a defect. This paper propose the electric characteristic variation and the power prediction of PV module with damaged bypass diode. Firstly, the resistance for normal bypass diode and damaged bypass diode of resistance was measured by changing the current. When the current increases, the resistance of normal bypass diode is almost constant but the resistance of damaged bypass diode increases. Next, To estimate power of PV module by damaged bypass diode, the equation for the current is derived using solar cell equivalent circuit. Finally, the derived equation was simulated by using MatLab tools, was verified by comparing experimental data.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.202-207
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• 2017

This paper presents the performance of a planar, low-profile, and wide-gain-bandwidth leaky-wave slit antenna in different thickness values of high-permittivity gallium arsenide substrates at terahertz frequencies. The proposed antenna designs consisted of a periodic array of $5{\times}5$ metallic square patches and a planar feeding structure. The patch array was printed on the top side of the substrate, and the feeding structure, which is an open-ended leaky-wave slot line, was etched on the bottom side of the substrate. The antenna performed as a Fabry-Perot cavity antenna at high thickness levels ($H=160{\mu}m$ and $H=80{\mu}m$), thus exhibiting high gain but a narrow gain bandwidth. At low thickness levels ($H=40{\mu}m$ and $H=20{\mu}m$), it performed as a metasurface antenna and showed wide-gain-bandwidth characteristics with a low gain value. Aside from the advantage of achieving useful characteristics for different antennas by just changing the substrate thickness, the proposed antenna design exhibited a low profile, easy integration into circuit boards, and excellent low-cost mass production suitability.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1025-1034
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• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.1
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• pp.7-12
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• 2008

The vacuum interrupter (VI) is used for medium-voltage switching circuits due to its abilities and advantages as a compacted environmental friendly circuit breaker. In general, the application of a sufficiently strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. A full understanding of the vacuum arc physics is very important since it can aid to improve the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, we have investigated the effect of changing geometrical parameters for electromagnetic behaviors of high-current vacuum arcs with two different types of AMP contacts, which are coil-type and cup-type, using a commercial finite element analysis (FEA) package, ANSYS. The present results are compared with those of MAXWELL 3D, a reliable electromagnetic analysis software, for verification.

• Tribology and Lubricants
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• v.11 no.5
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• pp.40-46
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• 1995

This study concerns the design and development of the non-vibrating capacitance probe which could be used as a non-contact sensor for tribological wear. This device detects surface charge through temporal variation in the work function of a material. Experiments are performed to demonstrate the operation of the probe on a roating aluminum shaft. The reference electrode of the probe, made of lead, is placed adjacent (< 1.25-mm distance) to the shaft. Both surfaces which are electrically connected, form a capacitor. An artificial spatial variation in the work function is imposed on the shaft surface by coating a segment along the shaft circumference with a colloidal silver paint. As the shaft rotates, the reference electode senses changing contact potential difference with the shaft surface, owing to compositional variation. Temporal variation in the contact potential difference induces a current through the electrical connection. This current is amplified and converted to a voltage signal by an electoronic circuit with an operational amplifier. The magnitude of the signal decreases asymptotically with the electrode-shaft distance and increases linearly with the rotational frequency. These results are consistent with the theoretical model. Potential applications of the probe on wear monitoring are proposed.