• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.3
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• pp.384-393
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• 2012

Railroad signaling systems perform controlling the distance and routes between trains. Signaling methods on the wayside are to control passively the train speed by using signal flags which are installed on the wayside. ATS(Automatic Train Stop) device is used as the signaling method on the wayside in Korea. The ATS device is assistance equipment of engineers. Signal information is transmitted by combining mutual inductance between the wayside transmitter and on-board receiver. The wayside transmitter performs changing oscillation frequency according to the signal information. The on-board receiver performs controlling the train by receiving the frequency. Currently, the oscillation frequency on the on-board receiver is 78[kHz] in case of normal state. When the on-board receiver is over the wayside transmitter, the oscillation frequency is changed by capacitors of the wayside transmitter according to signal flags. In case of changing the oscillation frequency, the waveform is modified in the wayside transmitter and on-board receiver. This phenomenon is that other signals or communication frequency are included. In this paper, electric model between the wayside transmitter and on-board receiver is suggested and frequency response in the wayside transmitter and on-board receiver including other signals is estimated by the coupling coefficient. Also, the value of coupling coefficient is proposed to exclude other signals and demonstrated by using Matlab and PSpice program.

• Smart Structures and Systems
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• v.13 no.4
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• pp.501-515
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• 2014

This paper presents a linear computational homogenization framework to evaluate the effective (or generalized) electromechanical coupling coefficient (EMCC) of adaptive structures with piezoelectric structural fiber (PSF) composite elements. The PSF consists of a silicon carbide (SiC) or carbon core fiber as reinforcement to a fragile piezo-ceramic shell. For the micro-scale analysis, a micromechanics model based on the variational asymptotic method for unit cell homogenization (VAMUCH) is used to evaluate the overall electromechanical properties of the PSF composites. At the macro-scale, a finite element (FE) analysis with the commercial FE code ABAQUS is performed to evaluate the effective EMCC for structures with the PSF composite patches. The EMCC is postprocessed from free-vibrations analysis under short-circuit (SC) and open-circuit (OC) electrodes of the patches. This linear two-scale computational framework may be useful for the optimal design of active structure multi-functional composites which can be used for multi-functional applications such as structural health monitoring, power harvest, vibration sensing and control, damping, and shape control through anisotropic actuation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.226-229
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• 2005

In this study, a step-down piezoelectric transformer was fabricated to utilize as an adapter for charging batteries of mobile electronic appliances. The ceramic part of the transformer is $Pb[(Mn_{1/3}Sb_{2/3})_{0.05}Zr_{0.475}Ti_{0.475}]O_3$ with mechanical quality factor of 1600, electromechanical coupling coefficient 59 %, and piezoelectric constant d33 1300, which can be utilized as a piezoelectric transformer. A simply fabricated disk-typed test pattern of diameter 28 mm and thickness 2 mm was used to characterize resonant frequency, Qm, kp according to the different input/output electrode area. efficiency and power as a function of load resistance was also investigated. The sample APT showed some spurious mode and BPT showed better frequency property. Taking all properties which are admittance, effective electromechanical coupling coefficient and mechanical quality factor most suitable for piezoelectric transformer is BPT which has 12 mm diameter electrode and the condition of 15 Vrms, 30 $\Omega$ made the maximum efficiency of 93.7 % and maximum power is 6W with 50 Vrms.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.48 no.9
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• pp.611-615
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• 1999

Piezoelectric properties of PMN-PZT ceramics with $CeO_2$ impurity were investigated. Mechanical quality factor, $Q_m$ of 1792, 1285 and the electromechanical coupling coefficient, $k_p$ of 0.52, 0.54 were obtained from the specimen with 0.25 and 0.5 mole % $CeO_2$ respectively. Curie temperature was decreased with the addition of $CeO_2$ while the electric coercive field was proportional to the amount of impurity. Based on the system ceramics with 0.5 mole % cerium oxide, a Rosen type piezoelectric transformer was fabricated and tested. Voltage step-up ratios of 230 and 13 were obtained from the transformer at no load and $100 k\Omega$ resistance, respectively. Experimental results showed a potential of the transformer for the practical use coupled with the expected strength increase by the grain size refinement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.11
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• pp.1007-1013
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• 2005

In this study, a step-down piezoelectric transformer was fabricated to utilize as an adapter for charging batteries of mobile electronic appliances. The ceramic part of the transformer is $Pb[(Mn_{1/3}Sb_{2/3})_{_0.05}Zr_{0.475}Ti_{0.475}]O_3$ with mechanical quality factor of 1600, electromechanical coupling coefficient $59\%$, and piezoelectric constant $d_{33}$ 1300, which can be utilized as a piezoelectric transformer. A simply fabricated disk-typed test pattern of diameter 28 mm and thickness 2 mm was used to characterize output voltage, step-down ratio as a function of electrode area with the input remained constant, and power, efficiency as a function of input voltage, and temperature-dependent electric characteristics were evaluated. The sample APT1 showed the best properties. The highest admittance, effective electromechanical coupling coefficient and an appropriate mechanical quality factor were obtained at the sample with the input/output area ratio of 1:1.5 at the common electrode, and the condition of 20 $V_{rms}$, $50\;\Omega$ made the maximum efficiency of $95\%$. The temperature was increased by 14.7'E as the input voltage was increased for $50\;V_{rms},\;50\;\Omega$.

• International Journal of Advanced Culture Technology
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• v.7 no.1
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• pp.225-230
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• 2019

In order to improve performance for the size of the rat-race ring coupler, the CCL is used for the realization as the delay line. As realizing lower coupling coefficient, the ratio of the size-reduction for the CCL is enhanced. The CCL is alternated with ${\lambda}_g/4$ of the rat-race ring, and optimized two CCLs are inserted for the size-reduction. the coupling coefficient is 0.2, and electrical lengths of each CCL are $28.2^{\circ}$ and $21.7^{\circ}$. Designed rat-race ring using the CCL has the size of $18.76{\times}20.45mm^2$ and the size-reduction ratio of fabricated rat-race ring using the CCL has 76.8%. Also, fabricated rat-race ring is measured the insertion loss of 3.20dB at the center frequency of 2.45GHz and the 20dB bandwidth is 24.04%. Differenced magnitude and phase between threw port and coupled port are measured 0.1dB and $177.4^{\circ}$, respectively. These performances are almost same compared with the conventional rat-race ring. Suggested application of the CCL can be used various devices and circuits for the size-reduction.

• Journal of IKEEE
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• v.27 no.1
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• pp.53-58
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• 2023

In this paper, a Radio Frequency (RF) transformer (TF) based on LTCC (Low Temperature Co-fired Ceramic) for the output stage of differential power amplifiers is presented. Instead of using an usual L-C matching circuit, a small-sized transformer was implemented on the LTCC board and the results were verified through simulation. For reduced size and better performance, a TF using more metal layers was implemented and compared with the existing TF through simulation. As a result of comparison, the proposed TF has an area reduced by 55% and a coupling coefficient increased by 25%, and insertion loss improvement of about 0.4dB at 5GHz was confirmed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.961-966
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• 2009

In this paper, a novel voltage-controlled oscillator(VCO) using the metamaterial broadside coupled spiral resonators(BC-DSRs) is presented for reducing the phase noise. For reducing of the phase noise, the series spiral structures have been applied for the signal plane and ground plane at each in order to have the large coupling. Compared with the conventional VCO, the proposed VCO has the larger coupling coefficient constant, which makes a higher Q-factor and has reduced the phase noise of the VCO. The proposed VCO has the phase noise of $-121{\sim}-117.16\;dBc$/Hz at 100 kHz in the tuning range, $5.749{\sim}5.853\;GHz$. The figure of merit(FOM) of this VCO is $-198.45{\sim}-194.77\;dBc$/Hz at 100 Hz in the same tuning range, respectively.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.6
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• pp.63-71
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• 1998

In this paper, we experiment the characteristics of coupling coefficient, gain, diffraction efficiency and dependence of time determined by TWM(Two-Wave Mixing), using Fe-LiNbO$_3$ crystal(doped with 0.015Wt.%). From these results, we proposed to apply for optical memory application. The highest coupling angle of 14。 and maximum coupling coefficient of 6.9$cm^{-1}$ / are obtained at 514.5nm wavelength. Also, maximum diffraction efficiency is 54.13% when intensity ratio and writing beam incident angle are 0.1 and 14o, respectively. After fixing process, diffraction efficiency is 21.4%. As an example, we demonstrated the writing and reconstruct optical data using spatial light modualtor and angular multiplexing in most optimal condition.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.5
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• pp.88-98
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• 1999

A refractive index modulated (RIM) DFB laser, in which the refractive index of a center region of the upper cladding layer comprising the grating region is different from that of side regions, is proposed to obtain and effective ${\lambda}$/4 phase shift in the center region. Since the coupling coefficient of a center region in a RIM-DFB laser is larger than that of side regions, a RIM-DFB laser has the effect of a distributed coupling coefficient. Simulation results show that RIM-DFB lasers have better operation characteristics - more uniform photon density profile, less SHB effect, and better single mode operation at high injection currents - compared to those of ${\lambda}$/4 phase-shifted DFB lasers and CPM-DFB lasers. In addition, the effect of the center region on the above threshold characteristics of a RIM-DFB laser is investigated.