• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.118-120
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• 2016

A coplanar waveguide employing periodic 3D coupling structures (CWP3DCS) was developed for application in miniaturized on-chip passive components on silicon radio frequency integrated circuits (RFIC). The CWP3DCS showed the shortest wavelength of all silicon-based transmission line structures that have been reported to date. Using CWP3DCS, a highly miniaturized impedance transformer was fabricated on silicon substrate, and the resulting device showed good RF performance in a broad band from 4.6 GHz to 28.6 GHz. The device as was 0.04 mm² in size, which is only 0.74% of the size of the conventional transformer on silicon substrate.

• 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.

• Journal of electromagnetic engineering and science
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• v.3 no.2
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• pp.104-110
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• 2003

A ring filter is proposed as a wide-banded filter. It consists of a ring and two short stubs, which are connected at 90$^{\circ}$ and 270$^{\circ}$ points of the ring. Since the termination impedance at 90$^{\circ}$ and 270$^{\circ}$ points of the ring and the characteristic impedance of the short stub have an effect on designing of it, the relation between them and bandwidths has been studied. Based on the study, two types of small-sized wideband CVT(constant VSWR-type impedance transformer)- and CCT(constant conductance-type impedance transformer)-ring filters are introduced, designed, simulated and one of two, a CCT -ring filter, is tested. The circumference of the ring can be reduced theoretically up to 60$^{\circ}$ and two of many cases having about 300$^{\circ}$ circumferences are simulated. The simulated results show more than 100 % fractional bandwidth, which can be obtained with more than 5 stages in conventional filter-design techniques. To test the designed CCT-ring filter, it has been fabricated in microstrip technology and the measured results show good agreement with the simulated ones, having more than 100 % fractional bandwidth.

• 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.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.9 no.5
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• pp.67-71
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• 2010

This paper proposes new dual-band impedance transformers based on the L-section circuit topology. The proposed circuits consist of a transmission line section with a stub line either at the source or at the load end. The dual-band operating conditions are analyzed in detail and simple design equations are derived in terms of the line lengths and impedances for the different circuit topologies and load conditions. The dual-band operation is confirmed through the design, fabrication and measurement in microstrip circuits based on the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1484-1491
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• 2020

Since the slot line transmits electric and magnetic signals through the slot, the size of the slot greatly affects the signal power loss. In order to have low loss, the slot line is mainly used at a high frequency of above 3GHz on a substrate having a high dielectric constant(er). This paper proposes the 4:1 impedance transformer using a slot line on TLC-30 laminate (h=20mil, er=3.0; Taconic) being a relatively low dielectric constant at a frequency of 1.85GHz. In the proposed impedance transformer, the dielectric resonator is arranged on the slot line to reduce signal loss occurring at the slot line. The proposed 4:1 microstrip-slot line impedance transformer fabricated using a (Zr,Sn)TiO4 dielectric resonator(er=38) has the transmission loss(S21) of -0.375dB and the reflection value(S11) of -27.6dB at 1.855GHz. This confirms that the slot line can be stably used even in a low dielectric constant substrate and a low frequency region by using a dielectric resonator.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.47-51
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• 2001

In this paper, we have explained electrical characteristics of a step-down Rosen type piezoelectric transformer for AC-adapter. When the electric voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, then output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. From the piezoelectric direct and converse effects, symbolic expressions between the electric inputs and outputs of the step-down piezoelectric transformer have derived with an equivalent circuit model. With the symbolic expressions, load and frequency characteristics have discussed through simulation. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformers were measured under the various conditions of loads and frequencies. First we measured resonant frequency from impedance curve and got equivalent impedance value of the piezoelectric transformer from admittance plot. It was shown from experiments that output voltage has increased and resonant frequency has changed according to various resistor loads. Output current has decreased inversely proportional to changing of loads. Moreover, the measured values of output voltage and current are well agreed with the simulated values of the proposed equivalent circuit model.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.469-475
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• 2017

Using impedance matching techniques as a way to increase system power transferability in capacitive wireless power transmission has been widely investigated in conventional studies. However, these techniques tend to increase the circuit volume and thus counterbalance the advantage of the simplicity in the energy link structure. In this paper, a compact circuit topology with one leakage-enhanced transformer is proposed in order to minimize the circuit volume for the capacitive power transfer system. This topology achieves a reactive compensation, and the system quality factor value can be reduced by the turn ratio. As a result, this topology not only reduces the overall system volume but also minimizes the voltage stress of the link capacitor. An optimal design guideline for the leakage-enhanced transformer is also presented. The advantages of the proposed scheme over the conventional method in terms of power efficiency and circuit volume are revealed through an analytic comparison. The feasibility of applying the new topology is also verified by conducting 50 W hardware tests.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.05c
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• pp.132-137
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• 2002

The mold transformers have been widely used in underground substations in large building and have some advantages in comparison to oil-transformer, that is low fire risk, excellent environmental compatibility, compact size and high reliability. In addition, the application of mold transformer for outdoor is possible due to development of epoxy resin. The mold transformer generally has cooling duct between low voltage coil and high voltage coil. A mold transformer made by one body molding method has been developed for small size and low loss. The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. In this paper, the temperature distribution of 50 kVA pole mold transformer for power distribution are investigated by FEM program and the temperature rise test of designed mold transformer carried out and test result is analyzed compare to simulation data. In this result, the designed mold transformer is satisfied to limit value of temperature and the other property is good such as voltage ratio, winding resistance, no-load loss, load loss, impedance voltage and percent regulation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.6
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• pp.932-937
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• 2008

The transformer inrush current can cause a voltage drop by source impedance. This current can impact sensitive loads by the voltage drop. Therefore, it is necessary to take measures to limit this inrush current. This study, described in this paper, analyzes the power quality affected by transformer inrush current using the X power system in Korea. The Electromagnetic Transients Program(EMTP) is used to analyze the transient phenomenon. We discuss a method to model the hysteresis curve of the transformer in EMTP. We carried out various simulations to analyze the power quality during transformer energization. The analysis results of voltage drop by the inrush current occurrence when certain requirements are met are presented.