• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.1236-1238
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• 2001

The electrified railway has various power supply schemes. Although the identical trains are operated in same condition and the impedance of track are equal, the genealogy impedance of track is changed according to composition method of feeding scheme. So, the collection voltage of train and supplying power from railway substation are greatly unlike. For simulation of collection voltage and power supply according to feeding scheme, using 6-port network analysis proposed previously simulate collection voltage and supply power according to feeding scheme(Parallel Post feeding system, normal feeding system and tie feeding system) and compare and investigate each characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.12
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• pp.1051-1057
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• 2000

A traveling-wave CPW(coplanar waveguide) electrode with abruptly broken input/output-taper for LiNbO$_3$optical modulator was designed and fabricated. The electrical characteristics of traveling-wave electrode on z-cut LiNbO$_3$crystal with SiO$_2$buffer layers were measured by network analyzer. To confirm the possibility of the electro-optic modulator electrode, detailed calculations of the impedance, microwave effective index and attenuation constants are presented as a function of the microwave electrode thickness, but the buffer layer thickness is fixed as 1${\mu}{\textrm}{m}$. These characteristics are discussed from the viewpoint of the device optimization and are expected to be design guides for the LiNbO$_3$modulator’s electrodes.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.6-8
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• 1993

Short Circuit analysis is one of the most fundamental procedures for power system analysis problem. In order 10 solve the problem, In order to solve the problem, it's required to develop an advanced algorithm by which modified bus admittance matrix are easily computed for a large number of alternative network configuration. This paper proposes a new calculation method to efficiently modify the bus impedance matrix elements of large power system by method for removal of link, and presents its Practicality by applying the proposed method in the power system model.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.290-292
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• 2002

In this paper, we present a simple design method and measurement results for circular loop antenna arrays, which can be used for LS band operation, such as access point antennas in the wireless LAN system. It has been shown that the input impedance of a circular loop can be adjusted near 100 $\Omega$ using a short stub. The length of the stub can be immediately determined in the work place through the measurement of S11 with a network analyzer. Fabricated arrays show high antenna gains as much as 12.4㏈i and 15.1 ㏈i at the center frequency of 2.45 ㎓ for 4${\times}$l and 4${\times}$2 array, respectively. These types of loop arrays can be fabricated at a low cost.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.4
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• pp.325-334
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• 1987

Microwave integrated circuit phase shifters have undergone remarkable development to satisfy the fast and precise phase control requirements for phased array antennas. It is shown how relection type phase shift circuits using PIN diode can be analyzed and implemented so as to derve design equations for any phase shift. The reflection properties are achieved by the use of an impedance transforming two-port network and the virtual matching impedance method. Experimental and theoretical performance of 2-bit hybrid phase shifter designed by this method are found to be in good agreement for each bit.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.13 no.6
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• pp.501-509
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• 1988

A new type toroidal core transformer for impedance matching for 30MHz~90MHz has been designed and fabricated. It is shown to be reasonably good characteristics that insertind loss was 1.2[dB], VSWR was 1:2.0 and 100[%] bandwidthe was achieved. It is expected that resulting transformer can be used to replace existing frequency selector type matching network because it is much more compact and relatively easy to contruct.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12B
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• pp.1754-1757
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• 2001

In this paper, a R-band hybrid amplifier with the coplanar waveguide(CPW) and the photonic bandgap(PBG) structure is designed and fabricated. The PBG and the CPW techniques are simultaneously employed in amplifier to improve the power added efficiency(PAE) and the IMD(Intermodulation Distortion) in R-band. In this paper, the PBG structures are optimized to obtain matching network. The output impedance of amplifier and the input impedance of PBG are matched to minimize the return loss. The PAE and the IMD were improved 15% and 4.5dB compared with the conventional amplifier, respectively.

• KIEE International Transaction on Systems and Control
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• v.2D no.2
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• pp.120-124
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• 2002

A new methodology is presented to diagnose faults in equipment plasma. This is accomplished by using neural networks as a pattern recognizer of radio frequency (rf) impedance match data. Using a match monitor system, the match data were collected. The monitor system consisted mainly of a multifunction board and a signal flow diagram coded by Visual Designer. Plasma anomaly was effectively represented by electrical match positions. Twenty sets of fault-symptom patterns were experimentally simulated with variations in process factors, which include rf source power, pressure, Ar, and $O_$2 flow rates. As an input to neural networks, two means and standard deviations of positions were used as well as a reflected power. Diagnostic accuracy was measured as a function of training factors, which include the number of hidden neurons, the magnitude of initial weights, and two gradients of neuron activation functions. The accuracy was the most sensitive to the number of hidden neurons. Interaction effects on the accuracy were also examined by performing a 2$^$4 full factorial experiment. The experiments were performed on multipole inductively coupled plasma equipment.

• Proceedings of the KIEE Conference
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• 2006.10a
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• pp.196-197
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• 2006

An effective method is described for monitoring the ground impedance of intelligent building and power system. Most of grounding system of buildings are interconnected to extensive grounding network of power line, signal and control line, telecommunication line, and etc. Therefore, the residual voltages of power frequency and its harmonics may have an significant influence on the accurate measurement of ground impedance. For eliminating the influence of residual voltage, we developed a test power source for generating the 110[Hz] square wave and used digital filtering method in this research.

• Journal of Electrical Engineering and Technology
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• v.2 no.1
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• pp.29-34
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• 2007

The input and output impedances in a low voltage distribution system is one of the most important matters for power line communication because from the viewpoint of communication, the attenuation characteristic of the high frequency signals is greatly caused by impedance mismatch during sending and receiving. The frequency range is from 1MHz to 30MHz. Therefore, this paper investigates the input and output impedances in order to understand the characteristic of high frequency signals in the low voltage distribution system between a pole transformer and an end user. For power line communication, the model of Korea's low voltage distribution system is proposed in a residential area and then the low voltage distribution system is set up in a laboratory. In the low voltage distribution system, S parameters are measured by using a network analyzer. Finally, input and output impedances are calculated using S parameters.