• Fire Science and Engineering
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• v.26 no.2
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• pp.11-16
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• 2012

In this paper, we analyzed damage patterns of a folder type mobile phone caused by microwave-irradiation, to find an accurate fire cause and to investigate deliberate broken of mobile phone for obtaining pecuniary advantage by deception. In order to analyze broken patterns, we irradiated a mobile phone with microwave using by 2.45 GHz microwave oven. Form the experiment results, damage patterns of mobile phone have been tendency toward heavy broken patterns depending on time of microwave-irradiated. Distinctively, folder hinge and intenna(Planar Inverted-F Antenna) were heavy broken in compare with battery, enclosure and so on. The enclosure of mobile phone became just thermo-metamorphism and the battery was not broken such as explosion.

• 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.

• Journal of the Semiconductor & Display Technology
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• v.16 no.2
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• pp.85-88
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• 2017

In this paper, we have designed and fabricated a RF-DC voltage multiplier for 5.8GHz microwave wireless power transmission. In order to obtain higher voltage, the RF-DC voltage multiplier with 10 diodes (D-10) and the receiver module with an antenna and BPF (Band Pass Filter) was manufactured. The measured and compared results show that the voltages of the proposed one are lower than those of the previous tripler module up to 40cm. However, the voltage of the proposed one with the voltage multiplier is higher than that of the tripler module at the distances of 45cm and 50cm due to the voltage multiplier with 10 diodes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.333-338
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• 2008

In this paper, a new NMOS current-mirror type bridge rectifier for driving RFID chips, whose minimum input voltage required to obtain the effective DC output voltage is low enough and whose power dissipation can be reduced than that of conventional one, is proposed. The designed rectifier is able to supply high enough and well-rectified DC voltages to drive RFID transponder chips for the frequency range of 13.56 MHz HF(for ISO 18000-3), 915 MHz UHF(fur ISO 18000-6), and 2.45 GHz microwave(for ISO 18000-4). Output characteristics of the proposed rectifier are analyzed with the high frequency equivalent circuit. And the circuitry method for effective reducing of the gate leakage current due to the increasing of operating frequency is also proposed theoretically. Using this method, the power consumption of $100\;{\mu}W$ and the DC output voltage of 2.13V for 3V peak-to-peak input voltage and $45\;K{\Omega}$ load resistance are obtained. Compared to conventional one, the proposed rectifier operates in more stable and shows superior characteristics in UHF and microwave frequencies.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.04a
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• pp.236-238
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• 1997

A cellular power amplifier using an APCVD(Atmospheric Pressure Chemical Vapor Deposition)-grown SiGe base HBT of ETRI has been designed with a linear simulation CAD. The Si/SiGe HBT with an emitter area of 2$\times$8${\mu}{\textrm}{m}$$^2$typically has a cutoff frequency(f$_{T}$) of 7.0 GHz and a maximum oscillation frequency(f$_{max}$) of 16.1 GHz with a pad de-embedding A packaged power Si/SiGe HBT with an emitter area of 2$\times$8$\times$80${\mu}{\textrm}{m}$$^2$typically shows a f$_{T}$ of 4.7 GHz and a f$_{max}$ of 7.1 GHz at a collector current (Ic) of 115 mA. The power amplifier exhibits a Forward transmission coefficient(S21) of 13.5 dB, an input and an output reflection coefficients of -42 dB and -45 dB respectively. Up to now the III-V compound semiconductor devices hale dominated microwave applications, however a rapid progress in Si-based technology make the advent of the Si/SiGe HBT which is promising in low to even higher microwave range because of lower cost and relatively higher reproducibility of a Si-based process.ess.ess.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.5 no.2
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• pp.135-141
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• 1995

Abstract The sintering behavior and the electrical properties of sintered PZT ceramics using 2.45 GHz microwave energy were investigated. The ceramics were sintered between $1050 ~ 1130^{\circ}C$ for 5 min. Sintered body with high density and good electrical properties were achieved as the sintering temperature increases. Above $1090^{\circ}C$, however, the bulk density was decreased due to the volatilization of PbO component, and also electrical properties were decreased. The relative dielectric constant, mechanical Quality factor, electro- mechanical coupling factor of microwave sintered body at $1090^{\circ}C$ without PbO atmosphere were 1900, 80, 0.53 respectively, which were comparable to conventional sintering values. The sintering process completed within 20 min using microwave hybrid energy. The processing time and the amount of energy con-sumption could be reduced by microwave hybrid energy assisted rapid sintering.

• Journal of Bio-Environment Control
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• v.32 no.3
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• pp.217-225
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• 2023

This experiment was conducted to investigate the effects of microwave irradiation on the growth and secondary metabolite contents of lettuce seedlings. Seedlings at three weeks after sowing were treated by a microwave oven for 0, 4, 8, and 12 seconds with 200 W. After cultivation in a close plant production system for 4 weeks, plant growth measurements and secondary metabolite analysis were performed. The results showed that the fresh and dry weights of the shoot and root, leaf area, leaf length, and the number of leaves were decreased as increasing the microwave treatment times. Chlorophyll a and b, total carotenoids were increased and total phenolics were decreased at the 12-second treatment compared to the 4-second treatment. Total flavonoid contents were decreased at the 8-second treatment compared to the control. These results suggest that the changes in the levels of secondary metabolites were caused by oxidative stress. Although there was no significant difference in secondary metabolite contents excluding total flavonoid contents on the microwave treatments compared to the control, the significant difference suggests that the microwave treatment of 200 W and 2.45 GHz may alter secondary metabolite contents of lettuce after 4 weeks.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.343-353
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• 1999

Microwave(2.45 GHz) was used as energy source in hydrothermal reaction to fabricate ultrafine BaTiO3 powder. Using microwave of 700 W, crytal BaTiO3 began to fom after 5 min in microwave-autoclave sys-tem. The crystallinity was not noticeably increased with increasing longer reaction time than 10 min. On the other hand in microwave-reflux system crytal BaTiO3 began to form after 15min and the crystallinity was not noticeably increased with increasing longer reaction time than 1hr,. In either case particle size dis-tribution was considerably uniform due to the effect of homogeneous heating by microwave. In addition mi-crowave heating gave an extremely small degree of particle agglomeration compared to electric heating. Av-erage sizes of as-synthesized powders were 30-60nm. Ba/Ti ratio in sol played an important role in det-ermining the particle size. It seems that excess barium forms different phases such as Ba(OH)2 which makes thin layer on the surface of BaTiO3 powder. This thin layer would inhibit the agglomeration of Ba-TiO3 powders and keep the small grain size. In microwave-autoclave system tetragonal-BaTiO3 was formed directly by the reaction of only 15 min. In the case of microwave-reflux system tetragonal-BaTiO3 was formed by driyng over 25$0^{\circ}C$.

• Journal of Advanced Navigation Technology
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• v.24 no.2
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• pp.107-114
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• 2020

A power amplifier of 2.4 GHz ISM band is designed to implement a transmitter system. High efficiency amplifiers can be implemented as class E or class F amplifiers. This study has designed a 20 W high efficiency class E amplifier that has simple circuit structure in order to utilize for the ISM band application. The impedance matching circuit was designed by class E design theory and circuit simulation. The designed amplifier has the output power of 44.2 dBm and the power added efficiency of 69% at 2.45 GHz. In order to apply 30 dBm input power to the designed power amplifier, voltage controlled oscillator (VCO) and driving amplifier have been fabricated for the input feeding circuit. The measurement of the power amplifier shows 43.2 dBm output and 65% power added efficiency. This study can be applied to the design of power amplifiers for various wireless communication systems such as wireless power transfer, radio jamming device and high power transmitter.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1630-1632
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• 1997

We have investigated activation phenomena of implanted ions on silicon wafers using microwave(2.45GHz). It is found that the higher concentration of impurities makes the better activation effects by microwave annealing. We have exposed poly-Si TFTs by microwave in order to anneal and improved the device performance. Microwave activates source/drain ions and lowers the contact resistance so that the current of the poly-Si TFTs increases. In addition, the leakage current of hydrogen passivated poly-Si TFTs is decreased after microwave annealing, due to the diffusion of hydrogen ions and curing the defects in the poly-Si active channel.