• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.739-747
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• 2007

Dual-mode bandpass filter was designed by using periodic stepped impedance ring resonator with step perturbation. The periodic stepped impedance ring resonator has the effects of size reduction and $2^{nd}$ harmonic suppression by changing characteristic impedance ratio. The perturbation for dual-mode generation was also easily controlled by characteristic impedance ratio, and the variation of dual-mode resonant frequencies and attenuation pole frequencies were analyzed by the effect of step perturbation. Chip capacitors were used for input/output coupling, and the variation of center frequency by the coupling capacitance and step perturbation was also considered. From the results, two types of 2 GHz dual-mode bandpass filter were fabricated in size of $14{\times}14mm^2$, those have different attenuation poles and bandwidths. The measured results of proposed bandpass filters showed a good agreement with the calculated estimations, and those have insertion loss of 2.52, 0.52 dB and 3 dB bandwidth of 4.03, 15.02 %, respectively.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.2
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• pp.153-159
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• 2008

We have developed an absolute evaluation method to obtain the ratio error and phase displacement of a current transformer (CT) without any precise standard CT by measuring four parameters in a CT equivalent circuit. The excitation admittance in the CT equivalent circuit can be obtained by employing standard resistors with negligible reactive component. The secondary leakage impedance in the CT equivalent circuit can be measured using a universal impedance bridge. The method was applied to CTs under test with the wide current ratios in the range of 5 A / 5 A - 5,000 A / 5 A and 5 A / 1 A - 5,000 A / 1 A. The ratio error and phase displacement of the CT under test obtained in this study are consistent with those measured at the national institute in Canada using the same CT under test within an expanded uncertainty (k = 2) in the overall current ratios.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.8
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• pp.403-407
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• 2006

Standard capacitors, as like as Hamon resistor standards, of series connection/parallel connection ratio $10{\mu}F/1000{\mu}F\;and\;100{\mu}F/10000{\mu}F$ were fabricated for calibration of impedance bridges or analyzers with measuring ranges up to 1 F. The calculated correction terms to the ratio of one measured value in series connection to the value in parallel connection were evaluated to be $1.92{\times}10^{-7}$. These capacitors were designed to be used not only as 100:1 capacitance standards but also as single capacitors or decade capacitors with decade values at frequencies up to 1 kHz.

• Journal of Advanced Navigation Technology
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• v.16 no.5
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• pp.781-786
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• 2012

In this paper, we propose the design and performance of an unequal divider using transmission line with periodic capacitor shunt connection. To design divider with a high dividing ratio, we limit a high impedance line value to fabricate microstrip line and also, design a low impedance line of below $10{\Omega}$ using periodic capacitor shunt connection. As a design example, a 10:1 ratio divider was designed and measured at center frequency 1 GHz to show the validity of the unequal divider using periodic capacitor shunt connection. Its performance is in good agreements with the simulated results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1626-1631
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• 2007

This paper presents a new modeling method using lamp output power and the modeling coefficients of the lamp. The proposed method utilizes the lamp modeling coefficients such as equivalent impedance Z(p), coupling coefficient of the transformer k(p), turns ratio of the transformer n(p), and plasma resistance Rp(p) as a function of lamp output power. The equivalent impedance Z(p) was developed from the equivalent resistance Req(p) and equivalent inductance Leq(p) of the lamp. Simulation and experimental results of the proposed model are presented in order to validate the proposed method. The modeling method can use to design an impedance matching circuit for a Class-D inverter.

• Journal of Sensor Science and Technology
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• v.12 no.5
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• pp.205-210
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• 2003

To develop the highly sensitive Magneto-Impedance sensor, the amorphous ribbon was micro-processed to meander type sensor pattern, and its external magnetic field dependence of impedance was investigated. The impedance of the pattern had peak value at the magnetic field of 13 Oe and its changing ratio was about 170%. The impedance change per unit magnetic field was about 36% at bias field of 6 Oe, in which the output with high sensitivity and linearity could be obtained. The magnetic field resolution of the sensor module, which consist of the amorphous pattern and driving circuit, was about $10^{-3}$ Oe.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.181-187
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• 2018

In this paper, sound absorption of micro-perforated elastic plates installed in an impedance tube of a circular cross-section is discussed using an analytic method. Vibration of the plates and sound pressure fields inside the duct are expressed in terms of an infinite series of modal functions, where modal functions in the radial direction is given in terms of the Bessel functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes, and the sound absorption coefficient is given in terms of an equivalent impedance of a single surface. The sound absorption coefficient using the proposed formula is in excellent agreement with the result by the FEM (Finite Element Method), and shows dips and peaks at the natural frequencies of the plate. When the perforation ratio is very small, the sound absorption coefficient is dominated by the vibration effect. However, when the perforation ratio reaches a certain value, the sound absorption is mainly governed by the rigid MPP (Micro-Perforated Plate), while the vibration effect becomes very small.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.327-332
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• 2018

In this paper, the value of inverter and the characteristics of the dual-mode resonator with the shunt-stub are analyzed and calculated. The value of inverter is function of the impedances and electrical lengths of the resonator and shunt-stub. According to suggested equation, the value of inverter is increased for the square root function. And the value of inverter is decreased as higher impedance of resonator and higher ripple. The bandwidth of the filter is increased as the ripple and the impedance ratio. Also, the center frequency of the filter is shifted as designed impedance. In order to show the designed method, the filter with the resonator's and stub's impedances of $70.7{\Omega}$, and $56.56{\Omega}$, respectively, is suggested by example.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.124-128
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• 1999

We report microwave properties of high-T$_c$ superconducting (HTS) microstrip antennas without impedance matching circuits, where the impedance mismatching is obvious under the critical temperature (T$_c$). The superconducting thin films used in this report were YBa$_2Cu_3O_{7-x}$ (YBCO) films deposited on MgO substrates produced by pulse laser deposition (PLD) technique. At around T$_c$, 86 K the reflection coefficient rapidly drops, and the standing wave ratio (SWR) becomes almost unity, and the characteristic impedance based on the Smith chart is nearly 50 ${\Omega}$. The reflection coefficient and the SWR of the HTS microstrip antenna were - 62.52 dB and 1.0015, respectively, at the resonant frequency of 11.812 CHz at 86 K.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.257-259
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• 2002

In investigating the characteristics of a neural network, the use of planar microelectrode array shows several advantages over normal intracellular recording[1]. A transparent indium tin oxide(ITO) multi-electrode array(MEA) was fabricated and its top surface was insulated with photodefinable polyimide(HD-8001) except the exposed area for interfacing between the ITO electrodes and the neuronal cells. The exposed ITO electrodes were platinized in order to reduce the impedance between the electrodes and electrolyte. The one-minute platinization with $0.99nA/{\mu}m^2$ current density reduced the average impedance of the electrodes from $2.5M\Omega\;to\;90k\Omega$ at 1kHz in normal ringer solution. Cardiac cells were cultured on this MEA as a pilot study before neuron culture. The signals detected by the platinized electrodes had larger amplitudes and improved signal to noise ratio(SNR) compared to non-platinized electrodes. It is clear that microelectrodes need to have lower impedance to make reliable extracellular recordings, and thus platinization is essential part of MEA fabrication. Burst spike of cultured olfactory bulb was also detected with the MEA having platinized electrodes.