• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.2
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• pp.329-334
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• 2016

In this paper, we demonstrate a Non-Foster matching method for an electrically small antenna to improve the signal-to-noise ratio (SNR) of communication link. For the experiment, we used a general FM antenna whose resonance frequency is about 52-57 MHz and a floating type Linvill negative impedance converter(NIC)-based circuit as a Non-Foster matching element. By implementing the Non-Foster circuit to cover FM band, we can achieve a wide bandwidth matching covers 40-200 MHz. Our measurement shows 3-7 dB improvement of SNR for the same bandwidth though there are several spikes which means no improvement of SNR in the band.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.490-491
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• 2007

We have investigated dielectric dispersion and absorption in organic light-emitting diodes using 8-hydroxyquinoline aluminum($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric dispersion and absorption of organic light emitting diodes using impedance characteristics measurement by the auto-balancing bridge technique of ITO/$Alq_3$/Al. Impedance characteristics was measured complex impedance Z and phase e in the frequency range of 40Hz to $10^8Hz$. We obtained dielectric constant and loss tangent (tan $\delta$) of the device. From these analyses, we are able to interpret a dielectric dispersion and dielectric absorption contributed by an interfacial and orientational polarization.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.534-540
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• 2005

This paper analyzes the correlations between the impedance matching of the antenna and the radiation characteristics of the mobile handset body. Using two kinds of mobile handset which has retractable and fixed antenna the impedance and radiation pattern is measured under totally 16 conditions. By measured results, it has been identified that the radiation energy into human head can be reduced by attaining the better impedance matching when the radiation pattern out of the mobile handset is like the ideal monopole antenna.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.215-218
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• 2007

In this paper, we have analyzed the effects from the change of separation distance between grounding equipment at end of telecommunication line and the inducting facilities in power inducting situation. In the result of measurement, we can see that as the separation distance between grounding equipment ant end of telecommunication line and the inducting facility become longer, the induced noise level and PIF level is decreased. From the another experiment results about the effect of changing the impedance size in both ends of telecommunication line, however, we already knew that as the ground impedance at either end of the telecommunication line become grower, the noise level is increased, and as the ground impedance at either end of the telecommunication line become smaller, the noise level is decreased. Hence we can not define the relationship exactly between separation distance from inducting facility to inducted facility and the induced noise level because when the grounding equipment is moved, its impedance size is changed too. In conclusion, changing the separation distance between grounding equipment at end of telecommunication line and the inducting facilities have not influence on the induced noise level.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.10
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• pp.793-797
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• 2010

The basic performance of the ground system is evaluated as the ground resistance by applying low frequency current below 1 kHz. However, characteristics of the ground system should be analyzed by high frequency current up to 1 MHz since transient currents having a few hundred kHz component flow during a line-to-ground fault and/or a lightning strike. This paper deals with the design and fabrication of a wideband ground impedance meter (WGIM) which measures the impedance of ground systems in ranges from 65 Hz to 1.28 MHz. Also, a noise elimination algorithm using a digital bandpass filter is proposed. The maximum error of the WGIM is 4.91% in the measurement frequency range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.320-321
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• 2006

In this work, impedance Spectroscopic analysis was applied to study the effect of plasma treatment on the surface of indium-tin oxide (ITO) anodes using $CF_4g$ as and to model the equivalent circuit for organic light emitting diodes (OLEDs) with the $CF_4$ plasma treatment of ITO surface at the anodes. This device with ITO/TPD/$Alq_3$/LiF/Al structure can be modeled as a simple combination of a resistor and a capacitor. The $CF_4$ plasma treatment on the surface of ITO shifts the vacuum level of the ITO as a result of which the barrier height for hole injection at the ITO/organic interface is reduced. The Impedance spectroscopy measurement of the devices with the $CF_4$ plasma treatment on the surface of ITO anodes shows change of values in parallel resistance ($R_p$) and parallel capacitance ($C_p$).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12A
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• pp.1136-1146
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• 2005

In this paper, the radiative electric field intensity due to the communication signal and conductive noise is calculated in overhead medium voltage power lines for power line communication. The input impedance is calculated by means of 2 port equivalent model of medium voltage power line network and basic transmission line theory. And then, currents is calculated by calculated input impedance and finally, the emissive electric field is calculated. The input impedance appears like a standing wave form with a fixed cycle because high reflection at the input terminal due to the characteristic impedance of medium voltage power line is very large. A calculated current and radiative electric field also appears like this form. From the measurement results, the measured results are very similar to the calculated results.

• Journal of IKEEE
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• v.23 no.4
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• pp.1473-1476
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• 2019

Accurate material information is very important in PCB (Printed Circuit Board) design. In an integrated mast of a battleship, heat reduction is essential for stealth functionality. So heat dissipation from internal control equipments should be reduced as much as possible. Control equipments mostly consist of PCBs, but it often suffers from impedance mismatching due to imprecise Dk (Dielectric Constant), which significantly increases heat dissipation. In this paper, measurement methods of Dk is investigated. Also, effects on impedance mismatch by Dk variation with operating frequency is investigated.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.731-734
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• 2002

This paper presents the assessment of input impedance of a sectoral cylindrical cavity-backed slot antenna excited by a probe. This antenna is proposed to be an element of array that can be assembled to be the antenna for UHF TV broadcasting system. The integral equations are derived based on boundary conditions of the proposed structure and are expressed in terms of dyadic Green's functions and unknown currents. The unknown current densities are solved by the Method of Moments and the input impedance is derived subsequently. Numerical results show the variation of input impedance, for the specified dimensions of the antenna, as a function of frequency. This result is validated by measurement and found that the result is sufficiently accurate. The result from this study is useful for the design of a sectoral cylindrical cavity-backed slot antenna excited by a probe.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2000.11b
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• pp.188-195
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• 2000

This study was conducted to measure the moisture content of powdered food using RF impedance spectroscopic method. In frequency range of 1.0 to 30㎒, the impedance such as reactance and resistance of parallel plate type sample holder filled with wheat flour and red-pepper powder of which moisture content range were 5.93∼-17.07%w.b. and 10.87 ∼ 27.36%w.b., respectively, was characterized using by Q-meter (HP4342). The reactance was a better parameter than the resistance in estimating the moisture density defined as product of moisture content and bulk density which was used to eliminate the effect of bulk density on RF spectral data in this study. Multivariate data analyses such as principal component regression, partial least square regression and multiple linear regression were performed to develop one calibration model having moisture density and reactance spectral data as parameters for determination of moisture content of both wheat flour and red-pepper powder. The best regression model was one by the multiple linear regression model. Its performance for unknown data of powdered food was showed that the bias, standard error of prediction and determination coefficient are 0.179% moisture content, 1.679% moisture content and 0.8849, respectively.