• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.5
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• pp.604-611
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• 2013

This paper presents an second harmonic elimination method based on the impedance variation scheme. Through the power quality analysis from the nonlinear loads connected on the power system, the second harmonic problems have been analyzed with a case study analysis and the experiments. In the paper, the second Harmonic generation was simulated with a single phase SCR rectifier and the analytical model is proposed for the second harmonic generation. A novel impedance variation scheme is proposed and analyzed to eliminate the second harmonic. The experiment has been performed on the 60(MVA) industry manufacturing plant. The experimental result demonstrates the proposed impedance variation scheme successfully operate on the 60(MVA) industry manufacturing plant.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.438-444
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• 2015

A new approach to the active phased arrays for the second harmonic generation is presented. Phase variation between the second harmonic oscillators by the mutual synchronization is analyzed theoretically. In this coupling, the active antenna consists of the FET oscillator which plays two roles in fundamental oscillation and frequency multiplying, and the patch antenna resonated at the second harmonic frequency. The radiated second harmonic wave was scanned by varying the free-running oscillation frequencies of the active antennas. In the experiment using the 2-elements array and the 4-elements array, the radiated beam of the second harmonic wave was scanned more widely compared with the case of the fundamental wave radiation.

• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.3
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• pp.257-263
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• 2013

Acoustic nonlinearity of surface waves is an effective method to evaluate the micro damage on the surface of materials. In this method, the $A_1$ (magnitude of the fundamental wave) and $A_2$ (magnitude of the second-order harmonic wave) are measured for evaluation of acoustic nonlinearity. However, if there is another source of second-order harmonic wave other than the material itself, the linear relationship between $A_1{^2}$ and $A_2$ will not be guaranteed. Therefore, the second-order harmonic generation by another source should be fully suppressed. In this paper, we investigated the initial second-order harmonic generation in narrowband surface waves by multi-line laser beams. The spatial profile of laser beam was considered in the cases of Gaussian and square-like. The temporal profile was assumed to be Gaussian. In case of Gaussian spatial profile, the generation of the initial second-order harmonic wave was inevitable. However, when the spatial profile was square-like, the generation of the initial second-order harmonic wave was able to be fully suppressed at specific duty ratio. These results mean that the multi-line laser beams of square-like profile with a proper duty ratio are useful to evaluate the acoustic nonlinearity of the generated surface waves.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.250-254
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• 1989

Second-harmonic generation at a silver-electrolyte (0.1 M KCL + H2O) interface was enhanced by surface roughness. The intensity of the second-harmonic radiation was shown to be sensitive enough to detect molecular monolayers adsorbed on a silver surface.

• Journal of electromagnetic engineering and science
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• v.8 no.3
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• pp.134-137
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• 2008

This paper proposes a novel quadrature VCO(QVCO) based on direct back-gate second harmonic coupling. The QVCO directly couples the current sources of the conventional LC VCOs through the back-gate instead of front-gate to generate quadrature signals. By the second harmonic injection locking, the two LC VCOs can generate quadrature signals without using on-chip transformer, or stability problem that is inherent in the direct front-gate second harmonic coupling. The proposed QVCO is implemented in $0.18{\mu}m$ CMOS technology operating at 2 GHz with 5.0 mA core current consumption from 1.8 V power supply. The measured phase noise of the proposed QVCO is - 63 dBc/Hz at 10 kHz offset, -95 dBc/Hz at 100 kHz offset, and -116 dBc/Hz at 1 MHz offset from the 2 GHz output frequency, respectively. The calculated figure of merit(FOM) is about -174 dBc/Hz at 1 MHz offset. The measured image band rejection is 46 dB which corresponds to the phase error of $0.6^{\circ}$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.8
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• pp.596-600
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• 1998

A method for the nondestructive read-out of the memory in ferroelectric thin films is demonstrated using the detection second harmonic currents introduced in the ferrolelectric capacitor as a response to an ac signal. The sign and phase of the second harmonic current depends on the polarized state +$P_r or -P_r$, The studied ferroelectric PZT thin film is found to have desirable features for the use as a memory element. This method and material seems as a promising approach for the nonvolatile memory storage.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.5
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• pp.173-180
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• 1984

The spectra of scattering light fromlaser-produced plasma near its fundamental and second harmonic wavelength were observed respectively by means of spectroscopic technique. The experimental results and the generation mechanism of nonlinear effects such as the second garmonics and the brillouin scattering were analysed theoretically. The spectra of reflected laser light became wider than that of incident laser light. And the peak of spectrum of reflected light shifted to red-side from that of incident light. The second harmonic light is generated from the nonlinear interaction of the incident laser light and the electron plasma wave excited in resonance region by the oblique incidence of laser light to the plasma. The Brillouin backscattering from laser-produced plasmas of hydrogen and deuterium has shown an isotope effect in the red-side region of the generated second harmonic light. This isotope shift is explained by the parametric instability at the cutoff (resonance) region using frequency-and phase-matching conditions of the waves.

• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.79-88
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• 2009

A harmonic quadrature demodulation method to extract the second harmonic component from focused ultrasound signals after a single transmit-receive event is proposed. In the proposed method, the focused ultrasound signal is converted into baseband inphase and quadrature components by multiplying with sine and cosine signals both having twice the center frequency of the transmitted signal and filtering the two modulated signals. The quadrature component is then passed through a Hilbert filter to be added to the inphase component, which leaves only the envelope of the second harmonic component. A novel phase estimation technique is employed in the proposed method to avoid the phase mismatch between the focused signal and the two modulating signals. The proposed method is verified through both theoretical analysis and computer simulations. It is shown that compared to the pulse inversion scheme the proposed method provides almost the same results for stationary targets and significantly improved harmonic to fundamental ratio for moving targets.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.12
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• pp.1700-1705
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• 2013

A second harmonic millimeter wave oscillator utilizing sub-harmonic injection-synchronization is presented. A 8.7GHz oscillator with MES-FET is designed, and is driven as a harmonic output oscillator at 17.4GHz by means of sub-harmonic injection-synchronization. The oscillator operates as a multiplier as well as a oscillator in this scheme. Adopting this method, a high sable, high frequency millimeter wave source is obtainable even though self-oscillating frequency of an oscillator is relatively low. The range of injection-synchronization is about 26MHz, and is proportional to the input sub-harmonic power. The spectrum analysis of the 2nd harmonic output frequency shows remarkably decreased the phase noise level.

• Korean Journal of Optics and Photonics
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• v.4 no.2
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• pp.206-211
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• 1993

We carried out the second harmonic generation of low power CW laser diode with maximum power of 30 mW in $LilO_3$ crystals. We used a ring enhancement cavity to increase the second harmonic conversion efficiency. The ring enhancement cavity was Composed of two flat mirrors and two concave mirrors. The focal length of concave mirrors was 25 mm, and 5 mm long and 10 mm long $LilO_3$ crystals were used. We measured the second harmonic power according to the pumping power and compared with theoretical value. We obtained 397 nm second harmonic power of about $6.6{\mu}W$ in 10 mm long $LilO_3$ crystal with the fundumental 794 nm pumping power of 28 mW.