• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.405-408
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• 2000

We designed and fabricated VCO using inductive reactance variation at 2GHz. A varactor diode is one of the main devices in VCO, which varies capacitance depending on reverse voltage. In this paper, a varactor diode is not used as a variable capacitive reactance device but as an inductive device. The circuit design and simulation have been carried out using HP-MDS. The fabricated VCO is measured using the HP 8532B spectrum analyzer and the HP 4352B VCO/PLL analyzer. The experimental result shows the phase noise -110dBc/Hz at a 100kHz offset frequency, the control voltage sensitivity of 23MHz/V and a -3.5dBm output power with a D.C. current consumption of 5.9mA. The simulation and measurements show exact agreement except with regard to the oscillation frequency. The measured oscillation frequency is lower than the simulation result because there is some parasitic inductance in the PCB layout.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.383-390
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• 2018

Piezoelectric micro-machined ultrasonic transducers for highly directional speaker need DC bias voltage. Most existing power amplifiers are not suitable for use in highly directional transducers because they are based on AC. In addition, since the piezoelectric micro-machined ultrasonic transducer has a large capacitive reactance, the power efficiency of the power amplifier is very low. Thus this paper proposes a new high efficiency power amplifier with DC bias voltage. In addition, by designing a matching circuit to compensate the capacitive reactance of the micro-machined ultrasonic transducer, the power efficiency of the power amplifier increases. The operating characteristics of the proposed power amplifier was verified by an experimental prototype. The proposed power amplifier is expected to be widely used in designing and implementing other related power amplifiers.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.329-338
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• 2001

In this paper, we designed microstrip patch antenna to enhance the weak point of general microstrip patch antenna that has narrow bandwidth and analyzed that. To reduce reactance in probe feed antenna, capacitive gap added to the patch. Using single patch and auxiliary wire, makes dual frequency resonant. So bandwidth is improved and gain also becomes higher. To verify with experiment, PCS band antenna is designed, fabricated. For PCS band antenna, bandwidth is 180 MHz in VSWR<1.5 and gain is 8.6 dBi.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.808-815
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• 2001

The three-phase diode rectifier with a capacitive filter is highly sensitive to line voltage unbalance, and may cause significantly unbalanced line currents even under slightly unbalanced voltage condition. This paper presents an analysis of this 'unbalance amplification' effect for an ideal rectifier circuit without ac-and dc-side inductors. The voltage unbalance is modeled by introducing a deviation voltage superimposed on balanced three-phase line voltages. With proper approximations, closed-form expressions for symmetrical components of the line current and current unbalance factor are derived in terms of the voltage unbalance factor, filter reactance, and load current. The validity of analytical predictions is confirmed by simulation.

• Proceedings of the IEEK Conference
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• 2000.06a
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• pp.267-270
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• 2000

The feasibility of small linear antenna for near range wireless communications was studied. The requirement of the system are frequency range 9∼12 MHz and antenna size 15 cm. The communication range is about 15 m. The antenna input impedance is very small radiation resistance and very large capacitive reactance. The lossless impedance matching is nearly impossible, therefore lossy matching is considered. The antenna has very low radiation efficiency. The near field calculation has a large uncertainty, but the results can be used as the guideline of a small linear antenna system for a near range wireless communication.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.202-204
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• 2000

This paper describes the theory and experimental result of scaled model of SSSC. The SSSC, a solid-state voltage source inverter coupled with a transformer, is connected in series with a transmission line. Injected voltage is almost in quadrature with the line current, thereby emulating an inductive or a capacitive reactance in series with the transmission line.

• Journal of Electrical Engineering and information Science
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• v.2 no.3
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• pp.95-98
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• 1997

A nonlinear optical-microwave interaction is carried out in an uniplanar CPW-to-Slotline ring resonator on the semi-insulating GaAs substrate, in which a Schottky photodetector is monolithically integrated as a coupling gap. When the capacitive reactance of the detetor is modulated, the parametric amplification effect of the mixer occurs. In this device structure, the parametric amplification gain of 20 dB without the applied bias in RF signal is obtained. This microwave optoelectronic mixer can be used in the fiber-optic communication link.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.638-647
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• 2003

Triangular patches have been studied, both theoretically and experimentally. We feund that provided radiation characteristics similar to those of rectangular patches, but with smaller size. In this paper, we designed an equilateral triangular microstrip patch antenna using cavity model analysis. Then, in order to improve narrow bandwidth, we add capacitive gap and air gap. Capacitive gap is located with square shape beside feeding point on the patch, and air gap is inserted between substrate dielectric and ground plane to adjust probe inductance. The analysis of characteristics and effects of each component was performed by commercial simulation tool, Ensemble 5.0. Throughout the simulation and experiment, we found the possibility of bandwidth enhancement in triangular microstrip antenna.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.135-138
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• 2004

Mobile phone antenna needs a small size and light weight for carrying and handling. In case of receiving a wide band TV signal, it would be difficult to obtain a good impedance matching between the antenna and the circuit due to a large capacitive reactance of antenna. Buffer amplifier was established on the teflon( ${\varepsilon}_r=3.38$, h=20mils) substrate by using GaAs FET( CPY30 ) and Silicon RF Transistor( BFP540 ) produced by Infineon and experimented.

• Proceedings of the KIEE Conference
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• 1998.11c
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• pp.776-778
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• 1998

Electrical and optical characteristics of Powder type EL display(P-ELD) in this study are described, In experimental results of V-J, current are increased with increasing the frequency and voltage. Luminance was increased with frequency. This is due to the positive space charge formed to cathode region. Lumiance at 150V, 20 kHz has $840\;cd/m^2$. This tendency is due to the decrease of capacitive reactance in insulator layer. Uniformity of P-ELD shows 97%. CIE chromaticity with increasing frequency are shifted toward blue color. It can be explained in tenn of the difference of recombination energy.