• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.3-7
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• 2004

An electric power efficiency of electrodeless fluorescent lamp has big relativie property of gas in lamp, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. We used magnetic substance that open self-examination material of electrodeless fluorescent lamp antenna. Ferrite that is used in this experiment was Mn-Zn type. We have examined resistance kind, impedance, Q-factor's frequency characteristic by ferrite. Impedance, resistance and capacitance did not show difference in start frequency 2.65 [MHz] but there was difference quantity. We could know Q-factor's difference according to material, and Q-factor's is important part of antenna design.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.7
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• pp.52-58
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• 2013

The two-dimensional finite difference time domain algorithm is used to numerically reconstruct the electron density profile in O-mode ultrashort pulse reflectometry. A Gaussian pulse is employed as the source of a probing electromagnetic wave. The Gaussian pulse duration is chosen in such a manner as to have its frequency spectrum cover the whole range of the plasma frequency. By using a number of numerical band-pass filters, it is possible to compute the time delays of the frequency components of the reflected signal from the plasma. The electron density profile is reconstructed by substituting the time delays into the Abel integral equation. As a result of simulation, the reconstructed electron density profile agrees well with the assumed profile.

• Current Optics and Photonics
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• v.2 no.1
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• pp.34-38
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• 2018

An X-band microwave photonic (MWP) filter using switch-based fiber-optic delay lines has been proposed and experimentally demonstrated. It is composed of two electro-optic modulators (EOMs) and $2{\times}2$ optical MEMS-switch-based fiber-optic delay lines. By changing time-delay difference and coefficients of each wavelength signal by using fiber-optic delay lines and an electro-optic modulator, respectively, a bandpass filter or a notch filter can be implemented. For an X-band MWP filter with four channel elements, fiber-optic delay lines with the unit time-delay of 50 ps have been experimentally realized and the frequency responses corresponding to the time-delays has been measured. The measured frequency response error at center frequency and the time-delay difference error were 180 MHz at 10 GHz and 3.2 ps, respectively, when the fiber-optic delay line has the time-delay difference of 50 ps.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.8
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• pp.26-33
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• 1992

This paper describes a new phase-difference detection method and the associate process algorithm for calculating the mean value of phase difference detected and OVCXO control value and for monitoring and controlling the DP-PLL operation status to be used in the design of a high-frequency DP-PLL. Through the experiments of DP-PLL implemented with 16-bit processor, memories, pheriperals and OVCXO to eraluate the suggested method and algorithm, it is shown that a remarkable improvement in PLL function such as phase detection, and reference clock tracing capability, jitter absorbability and frequency stability compared with other existing DP-PLL synchronization device is achieved.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.169-173
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• 2016

Terahertz (THz) generation by a GaP ridge waveguide with a collinear modal phase-matching scheme based on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascaded Stokes interaction processes and the cascaded anti-Stokes interaction processes are investigated from coupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared with non-cascaded DFG processes, THz intensities from 11-order cascaded DFG processes are increased to 5.48. The quantum conversion efficiency of 177.9% in cascaded processes can be realized, exceeding the Manley-Rowe limit.

• Current Optics and Photonics
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• v.1 no.2
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• pp.138-142
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• 2017

Terahertz (THz) generation by periodically-poled $KTiOPO_4$ (PPKTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascaded Stokes interaction processes and the cascaded anti-Stokes interaction processes are investigated from coupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared with non-cascaded DFG processes, THz intensities from 10-order cascaded DFG processes are increased to 5.53. The quantum conversion efficiency of 479.4% in cascaded processes, which exceeds the Manley-Rowe limit, can be realized.

• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.153-156
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• 2004

An electric power efficiency of electrodeless fluorescent lamp has big relative property of gas in lamp, gas pressure, lamp formation, ingredients of magnetic substance and shape and action frequency etc. We used magnetic substance that open self examination material of electrodeless fluorescent lamp antenna. Ferrite that is used in this experiment was Mn-Zn type. We have examined resistance kind, impedance, Q-factor's frequency characteristic by ferrite. Impedance, resistance and capacitance did not show difference in start frequency 2.65 [MHz] but there was difference quantity. We could know Q-factor's difference according to material, and Q-factor's is important part of antenna design.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.3
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• pp.23-30
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• 1985

When a digital filter implementation is based on a difference equation, the frequency characteristics cannot be obtained by direct computation, but be obtained by experiment or analogized by Z-transform. In this paper, the method to compute the frequency magnitude response of the function expressed in a difference equation is derived from PARSEVAL's relation. To verify the validity of this new method two types of digital filters are implemented. Both filters' characteristics are measured and their values are compared with the value obtained by a Z-transform and with the value by a difference equation. The result shows that the measured values and the values obtained by the difference equaton are more closer than the values by a Z-transform. And the difference-equaton-based filters' showed sharper roll off characteristics than the Z-transform-based filters. Therefore when a digital filter implementation is based on a difference equation, the characteristics computation by a difference equation predicts better practical results than based on Z-transform.

• The Journal of the Acoustical Society of Korea
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• v.32 no.4
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• pp.294-300
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• 2013

In this paper, we present performance analysis results of parametric array communication system in terms of theoretical BER and channel capacity of MIMO in underwater AWGN channel by using simplified SNR of difference frequency. The SNR of the difference frequency is calculated by using transmission loss, noise level, and source level of difference frequency in which nonlinear effect is considered. By assuming primary frequencies as 210 kHz and 190 kHz, difference frequency as 20 kHz, transducer diameter as 0.1 m, and noise level as 50 dB and the requested BER as $10^{-4}$, we obtain parametric array communication range gains over the communication system using primary frequency of 59.11 km in fresh water and 5 km in sea water, respectively. Also we obtain range gains of 38.84 km and 46.38 km in fresh water, and 3.88 km and 4.38 km in sea water when we use SISO and $2{\times}2$ MIMO parametric array communications for the channel capacity of 10 bps/Hz.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.154-159
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• 2019

When measuring the radiating noise of an underwater moving source, the range information between the acoustic source and the receiver is an important evaluation factor, and the measurement standards such as a receiver position, a moving source depth and a speed are set. Although there is a method of using the cross correlation as a method of finding the range of the underwater moving source, this method requires a time synchronization process. In this paper, we proposed the method to estimate the range by comparing the Doppler frequency difference of the theoretically calculated multipath signal with the Doppler frequency difference of the multipath signal estimated from the received signal. The proposed method does not require a separate time synchronization process. Simulations were performed to verify the performance, and the ranging error of the proposed method reduced by about 95 % than that of the conventional method.