• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.68-71
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• 2021

In this paper, GaN-SBD devices with excellent breakdown voltage and frequency characteristics for use in high-power microwave wireless power transmission has been modeled for PSpice circuit simulation. The RF-DC conversion circuits were simulated and compared with a commercial Si-SBD device. Although the modeled GaN-SBD devices had lower RF-DC conversion efficiency compared to Si-SBD at 2.4 and 5.8 GHz, it was confirmed through PSpice circuit simulations that they can be used sufficiently according to the required application circuit in a high power situation.

• Journal of the Semiconductor & Display Technology
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• v.15 no.4
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• pp.22-26
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• 2016

In this paper, we measured the efficiency of the receiver for 5.8GHz Microwave Smartphone Charging. We have designed and fabricated 1W and 2W power amplifier, respectively. A 1W power amplifier used a TC3531 power device of TRANSCOM Inc. In addition, a 2W power amplifier using the two TC3531 devices was constructed with divider and combiner. We used the Wilkinson divider theory for divider and combiner. The voltage was measured using the 1W and 2W power amplifier and integrated receivers to the distance of 50cm.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1385-1390
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• 2011

A coaxial-conical-radial transmission line conversion circuits have been investigated to realize a low loss high performance microwave power divider/combiner. In order to optimize the characteristics of the device, the power divider/combiner was designed separately with two parts-the inner part and the outer part. Utilizing the rectangular approximation of the outer part, we can design the low loss device which is not affected by the partition number N of the outer part. The small return loss which is lower than 20dB was obtained on the frequency range of 5.15GHz(7.45~12.60GHz). A conical connector was employed for smooth connection between the central coaxial line and the outer radial line. Making use of the $47^{\circ}$ and $90^{\circ}$ 2-stage conical connector, the return loss lower than 30dB was obtained on the operating frequency range of 5GHz. The total return loss of the designed divider/combiner was lower than 20dB on the frequency range of 5GHz for the partition number N=11, N=12 and N=16.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.498-498
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• 2013

Atmospheric Pressure Plasmas have pioneered a new field of plasma for biomedical application bridging plasma physics and biology. Biological and medical applications of plasmas have attracted considerable attention due to promising applications in medicine such as electro-surgery, dentistry, skin care and sterilization of heat-sensitive medical instruments [1]. Traditional approaches using electronic devices have limits in heating, high voltage shock, and high current shock for patients. It is a great demand for plasma medical industrial acceptance that the plasma generation device should be compact, inexpensive, and safe for patients. Microwave-excited micro-plasma has the highest feasibility compared with other types of plasma sources since it has the advantages of low power, low voltage, safety from high-voltage shock, electromagnetic compatibility, and long lifetime due to the low energy of striking ions [2]. Recent experiment [2] shows three-log reduction within 180-s treatment of S. mutans with a low-power palm-size microwave power module for biomedical application. Experiments using microwave plasma are discussed. This low-power palm-size microwave power module board includes a power amplifier (PA) chip, a phase locked loop (PLL) chip, and an impedance matching network. As it has been a success, more compact-size module is needed for the portability of microwave devices and for the various medical applications of microwave plasma source. For the plasma generator, a 1.35-GHz coaxial transmission line resonator (CTLR) [3] is used. The way of reducing the size and enhancing the performances of the module is examined.

• Journal of Electrical Engineering and Technology
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• v.7 no.6
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• pp.954-958
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• 2012

This paper reports a flexible patch rectenna for wireless actuation of cellulose electro-active paper actuator (EAPap). The patch rectenna consists of rectifying circuit layer and ground layer, which converts microwave to dc power so as to wirelessly supply the power to the actuator. Patch rectennas are designed with different slot length at the ground layer. The fabricated devices are characterized depending on different substrates and polarization angles. The EAPap integrated with the patch rectenna is actuated by the microwave power. Detailed fabrication, characterization and demonstration of the integrated rectenna-EAPap actuator are explained.

• Journal of IKEEE
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• v.22 no.3
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• pp.846-849
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• 2018

Wireless power transfer (WPT) is the technology that enables the power to transmit electromagnetic field to an electrical load without the use of wires. There are two kinds of magnetic resonant coupling and inductive coupling ways transmitting from the source to the output load. Compared with microwave method for energy transfer over a long distance, the magnetic resonance method has the advantages of reducing the barrier of electromagnetic wave and enhancing the efficiency of power transmission. In this paper, the wireless power transfer circuit having a resonant frequency of 13.45 MHz for the low power system is studied, and the hardware implementation is accomplished to measure the power transmission efficiency for the distance between the transmitter and the receiver.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.4
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• pp.567-572
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• 2015

Discharge characteristics of linear microwave plasma were investigated by using fluid simulation of 2D axis-symmetry based on finite elements method. The microwave power was 2.45 GHz TEM mode and transmitted through linear antenna. Resistive power and pressure were considered simulation variables and argon was used for working gas. A decrease of electron density along the quartz tube was observed in low power condition but relatively uniform plasmas were generated in chamber by increasing the resistive power. The electron temperature was highly detected near the surface of quartz tube because the electron was heated only dielectric surface. The power transmission efficiency decreased and characteristics of surface plasma were observed in high electron density condition.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.268-268
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• 2012

Atmospheric pressure microwave induced plasmas are used to excite and ionize chemical species for elemental analysis, for plasma reforming, and for plasma surface treatment. Microwave plasma differs significantly from other plasmas and has several interesting properties. For example, the electron density is higher in microwave plasma than in radio-frequency (RF) or direct current (DC) plasma. Several types of radical species with high density are generated under high electron density, so the reactivity of microwave plasma is expected to be very high [1]. Therefore, useful applications of atmospheric pressure microwave plasmas are expected. The surface characteristics of SUS304 stainless steel are investigated before and after surface modification by microwave plasma under atmospheric pressure conditions. The plasma device was operated by power sources with microwave frequency. We used a device based on a coaxial transmission line resonator (CTLR). The atmospheric pressure plasma jet (APPJ) in the case of microwave frequency (880 MHz) used Ar as plasma gas [2]. Typical microwave Pw was 3-10 W. To determine the optimal processing conditions, the surface treatment experiments were performed using various values of Pw (3-10 W), treatment time (5-120 s), and ratios of mixture gas (hydrogen peroxide). Torch-to-sample distance was fixed at the plasma edge point. Plasma treatment of a stainless steel plate significantly affected the wettability, contact angle (CA), and free energy (mJ/$m^2$) of the SUS304 surface. CA and ${\gamma}$ were analyzed. The optimal surface modification parameters to modify were a power of 10 W, a treatment time of 45 s, and a hydrogen peroxide content of 0.6 wt% [3]. Under these processing conditions, a CA of just $9.8^{\circ}$ was obtained. As CA decreased, wettability increased; i.e. the surface changed from hydrophobic to hydrophilic. From these results, 10 W power and 45 s treatment time are the best values to minimize CA and maximize ${\gamma}$.

• Journal of electromagnetic engineering and science
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• v.17 no.4
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• pp.191-196
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• 2017

Microwave wireless power transmission (MWPT) is a promising technique for low and medium power applications such as wireless charging for sensor network or for biomedical chips in case with long ranges or in dispersive media such. A key factor of the MWPT technique is its efficiency, which includes the wireless power transmission efficiency and the radio frequency (RF) to direct current (DC) voltage efficiency of RF-DC converter (which transforms RF energy to DC supply voltage). The main problem in designing an RF-DC converter is the nonlinear characteristic of Schottky diodes; this characteristic causes low efficiency, higher harmonics frequency and a change in the input impedance value when the RF input power changes. In this paper, rather than using harmonic termination techniques of class E or class F power amplifiers, which are usually used to improve the efficiency of RF-DC converters, we propose a new method called "optimal input impedance" to enhance the performance of our design. The results of simulations and measurements are presented in this paper along with a discussion of our design concerning its practical applications.

• Journal of the Semiconductor & Display Technology
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• v.17 no.2
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• pp.20-25
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• 2018

In this paper, we have designed circularly polarized array antenna for 5.8GHz microwave wireless power transmission. To obtain high antenna gain, we studied a single patch antenna, a $2{\times}1$ array antenna, a $2{\times}2$ array antenna, a $2{\times}4$ array antenna, and a $4{\times}4$ array antenna. Commonly, characteristics of each antenna have a frequency of 5.8 GHz and Right Hand Circular Polarization(RHCP) of circular polarization. Also, the results were obtained with the design to each antenna that the return loss was less than -10dB and the axial ratio was less than 3dB. The gain of the antennas was 6.08dBi for a single patch antenna, 9.69dBi for a $2{\times}1$ array antenna, 12.99dBi for a $2{\times}2$ array antenna, 15.72dBi for a $2{\times}4$ array antenna and 18.39dBi for a $4{\times}4$ array antenna. When the elements of the array antenna were increased, it was confirmed that it increased by about 3dBi.