• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1248-1256
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• 2008

In this paper, basic characteristics of transmission line employing PPGM (periodically perforated ground metal) were investigated using theoretical and experimental analysis.According to the results, unlike the conventional PBG (photonic band gap) structures, the characteristic impedance of the transmission line employing PPGM structure showed a real value, which exhibited a very small dependency on frequency. The transmission line employing PPGM structure showed a loss (per quarter wave length) higher by $0.1{\sim}0.2\;dB$ than the conventional microstrip line. According to the investigation of the dependency of RF characteristic on ground condition, the RF characteristic of the transmission line employing PPGM structure was hardly affected by the ground condition in the frequency lower than Ku band, but fairly affected in the frequency higher than Ku band, which indicated that coplanar waveguide employing PPGM structure was optimal for RF characteristic and reduction of size. Considering above results, impedance transformer was developed using coplanar waveguide with PPGM structure for the first time, and good RF characteristics were observed from the impedance transformer. In case that {\lambda}/4$ impedance transformer with a center frequency of 9 GHz was fabricated for a impedance transformation from 20 to10 {\Omega}$, the line width and length were 20 and $500\;{\mu}m$, respectively, and its size was only 0.64 % of the impedance transformer fabricated with conventional microstrip lines. Above results indicate that the transmission line employing PPGM is a promising candidate for a development of matching and passive elements on MMIC.

• 대한전기학회논문지:시스템및제어부문D
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• 제53권5호
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• pp.345-352
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• 2004

Currently, high data rate PLC(Power Line Communications), up to 100 Mbps, which use frequency bandwidth between 2 MHz and 30 MHz is investigated very hard, and commercial PLC modem for low voltage powerline network (indoor) is coming soon into communication market. For the purpose of developing a fit communication system which has little distortion of signal and attenuation, it is surely necessary to know about channel environments of powerline. Especially, the impedance measurement of the powerline and impedance matching are very important. As is known, since medium-voltage powerline (22.9 ㎸) is still working, it is not so simple to measure the powerline impedance. In our study, a portable impedance measurement equipment is developed. It consists of coupling capacitor, a drain coil and impedance matching transformer. The equipment is easily connected to medium voltage line and impedance of power line is measured using a network analyzer. Also, measurement results are used for impedance matching of PLC signal. In fact, matching transformer with several different impedances are used. The matching transformer is connected between coupling capacitor and signal port. In this paper, the developed portable impedance measurement equipment and impedance measurement results are presented. Also impedance matching technique using matching transformers will be explained. We showed the result of the improved performance by the impedance matching.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제11B권3호
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• pp.98-103
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• 2001

This paper presents the numerical analysis of piezoelectric devices using three-dimensional finite element analysis. The characteristic of piezoelectric transducer, such as mechanical displacement and electrical are analyzed and the validity is confirmed by experiments Applying the finite element routine to a piezoelectric transformer, the resonance features electrical impedance. the ratio of step-up voltage and vibration mode of piezoelectric transformer are calculated numerically By using three-dimensional finite element method effects of width variation to resonance features, electrical input impedance and the voltage step-up ratio for a piezoelectric transformer, can be considered in design procedure.

• 전기학회논문지
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• 제58권8호
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• pp.1479-1484
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• 2009

The introduction of the large transformer due to the large power demand has increased the fault current in power distribution system. The increased fault current can exceed the cut-off ratings of the circuit breaker. As the methods to solve this problem, the superconducting fault current limiter(SFCL) has been notified. However, the limited fault current by SFCL affects the operational characteristics of the protective device such as overcurrent relay. Therefore, the selection of the proper impedance for the SFCL is required to keep overcurrent relay's protective coordination with the SFCL when a large transformer is introduced into the distribution system. In this paper, the SFCL's impedance for protective coordination was investigates in that a large transformer is introduced.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 전기학술대회논문집
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• pp.417-422
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• 2005

Using the novel microstripline with periodically perforated ground metal, a miniaturized 1/4 ${\lambda}$ transformer was fabricated. The line width of the 1/4 ${\lambda}$ transformer was 20${\mu}m$ and the size of it was 0.0085$mm^2$, which is 1.2% of conventional one. The 1/4 ${\lambda}$ transformer exhibited good RF performances from 10 to 25GHz.

• Transactions on Electrical and Electronic Materials
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• 제16권1호
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• pp.10-15
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• 2015

A thin-film transmission line (TFTL) employing a microstrip line/coplanar waveguide (ML/CPW) was fabricated on a silicon substrate for application to a miniaturized on-chip RF component, and the RF characteristics of the device with the proposed structure were investigated. The TFTL employing a ML/CPW composite structure exhibited a shorter wavelength than that of a conventional coplanar waveguide and that of a thin-film microstrip line. When the TFTL with the proposed structure was fabricated to have a length of ${\lambda}/8$, it showed a loss of less than 1.12 dB at up to 30 GHz. The improvement in the periodic capacitance of the TFTL caused for the propagation constant, ${\beta}$, and the effective permittivity, ${\varepsilon}_{eff}$, to have values higher than those of a device with only a conventional coplanar waveguide and a thin film microstrip line. The TFTL with the proposed structure showed a ${\beta}$ of 0.53~2.96 rad/mm and an ${\varepsilon}_{eff}$ of 22.3~25.3 when operating from 5 to 30 GHz. A highly miniaturized impedance transformer was fabricated on a silicon substrate using the proposed TFTL for application to a low-impedance transformation for broadband. The size of the impedance transformer was 0.01 mm2, which is only 1.04% of the size of a transformer fabricated using a conventional coplanar waveguide on a silicon substrate. The impedance transformer showed excellent RF performance for broadband.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 C
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• pp.1760-1762
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• 2002

In this work we develop an equivalent circuit model of TCP(transformer coupled plasma) source and investigate matching characteristic. The developed circuit model includes transmission line, standard-type impedance matching network and displacement current in the plasma source. The impedance of TCP is calculated by previously developed program for various source parameters and dependance of components of matching impedance on the value of source impedance is investigated.

• 한국전자통신학회논문지
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• 제18권4호
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• pp.595-600
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• 2023

본 논문에서는 λ/4 전송선로의 T형 등가회로를 응용하여 임의의 길이를 갖는 전송선로에 대한 T형 등가회로를 제안하였다. 또한, 동일한 선로 길이라는 제한 없이 등가회로의 스터브의 위치를 조정할 수 있도록 수식을 만들어 등가회로의 활용도를 높이고자 하였다. 또한, 제안된 T형 등가회로는 λ/4 전송선로 뿐만 아니라 임의의 선로 길이 및 임피던스를 갖는 경우에도 적용할 수 있다. 제안된 T형 등가회로의 활용 예로 4 분할된 T형 등가회로를 갖도록 구성하여 λ/4 임피던스 변환기에 적용하였다. 변형된 임피던스 변환기는 0.15λ로 설계되어 39.4%의 크기 감소율을 보였다.

• 반도체디스플레이기술학회지
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• 제6권2호
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• pp.29-33
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• 2007

Low frequency (400 kHz) Ferrite ICP has been proposed for large area processing. Because the coupling coefficient is close to 1, the transformer matching can be adapted to Ferrite ICP. The transformer matching system is simple. In this paper the new matching system by controlling the turns of transformer using relays is proposed for impedance matching. We developed a simple matching system and characterized it when the turns were changed. It was observed that the 2-channel relay is available for transformer matching.

• 전기학회논문지
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• 제66권9호
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• pp.1334-1340
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• 2017

In this paper, a tie-plate shape is optimized by using the numerical technique to reduce the stray load loss of the tie-plate which is a mechanical structure for assembling and supporting of the transformer core. The eddy current loss of the structure is calculated by an electromagnetic field FEM program and the results are compared with 4 different shapes of tie-plates. Since the thickness of the tie-plate is very thin, and the skin depth is very small, the number of FE elements for 3-D transformer model is too big to solve. So, the surface impedance boundary condition (SIBC) is used to reduce the system matrix size and its computing time. To verify the method a 2.5 MVA 22,900/380V distribution transformer is simulated using one objective function and three design variables with some constraints. The final optimized tie-plate has three slots of 6 mm width and 23 mm gap, and the loss is reduced by 75 %. Consequently, the proposed algorithm seems to be considerably applicable to electric machinery as well as power transformer.