• Current Optics and Photonics
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• v.5 no.3
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• pp.213-219
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• 2021

We describe a single-channel rubidium (Rb) radio-frequency atomic magnetometer (RFAM) as a receiver that takes magnetic signal resonating with Zeeman splitting of the ground state of Rb. We optimize the performance of the RFAM by recording the response signal and signal-to-noise ratio (SNR) in various parameters and obtain a noise level of 159 $fT{\sqrt{Hz}}$ around 30 kHz. When a resonant radiofrequency magnetic field with a peak amplitude of 8.0 nT is applied, the bandwidth and signal-to-noise ratio are about 650 Hz and 88 dB, respectively. It is a good agreement that RFAM using alkali atoms is suitable for receiving signals in the very low frequency (VLF) carrier band, ranging from 3 kHz to 30 kHz. This study shows the new capabilities of the RFAM in communications applications based on magnetic signals with the VLF carrier band. Such communication can be expected to expand the communication space by overcoming obstacles through the high magnetic sensitive RFAM.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.144-145
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• 2009

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the poly crystal source of $CdGa_2Se_4$ at $630\;^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction (DCXD). The carrier density and mobility of single crystal $CdGa_2Se_4$ thin films measured with Hall effect by van der Pauw method are $8.27\;\times\;10^{17}\;cm^{-3}$, $345\;cm^2/V{\cdot}s$ at 293 K, respectively. The photocurrent and the absorption spectra of $CdGa_2Se_4$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 2.6400 eV - ($7.721\;{\times}\;10^{-4}\;eV/K)T^2$/(T + 399 K). Using the photocurrent spectra and the Hopfield quasi cubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) for the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_1$-, $B_1$-, and $C_{11}$-exciton peaks.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.337-337
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• 2013

ZnO seed layers were deposited on a quartz substrate using the sol-gel method, and B-doped ZnO (BZO) nanorods with different B concentrations ranging from 0 to 2.5 at.% were grown on the ZnO seed layers by the hydrothermal method. The structural, optical, electrical propertiesof the ZnO and BZO nanorods were investigated using field-emission scanning electron microscopy, X-ray diffraction (XRD), photoluminescence (PL), ultraviolet-visible spectroscopy, and hall effect. The ZnO and BZO nanorods grew well aligned on the surface of the quartz substrates. From the XRD data, it can be seen that the B doping is responsible for the distortion of the ZnO lattice. The PL spectra show near-band-edge emission and deep-level emission, and they also show that B doping significantly affects the PL properties of ZnO nanorods. The optical band gaps are changed by B doping, and thus the Urbach energy value changed with the optical band gap of the ZnO nanorods. From the hall measurements, it can be observed that the values of electrical resistivity, carrier concentration, and mobility are changed by B doping.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.124-125
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• 2007

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy (HWE) system by evaporating the polycrystal source of $CdGa_2Se_4$ at $630^{\circ}C$ prepared from horizontal electric furnace. The photocurrent and the absorption spectra of $CdGa_2Se_4$/SI(Semi-Insulated) GaAs(100) are measured ranging from 293K to 10K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$, obtained from the absorption spectra was well described by the Varshni's relation, $E_g$(T) = 2.6400 eV - $(7.721{\times}10^{-4}\;eV/K)T^2$/(T + 399 K). Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy$({\Delta}cr)$ and the spin-orbit splitting energy$({\Delta}so)$ for the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{11^-}$ exciton peaks.

• Journal of Korean Ophthalmic Optics Society
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• v.4 no.2
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• pp.97-103
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• 1999

Zinc sulfide is a ll-VI compound with a large direct band gap in the near-UV region and a promising material for blur-light emitting diode and laser diode. It was identified that the structure had zinc blonde structure through the analysis of X-ray diffraction patterns. It's lattice constant was measured to be $a_o=5.411{\AA}$. The optical absorption, photocurrent, and photoluminescence spectra were measured to investigate the optical properties of zinc sulfide single crystal. The optical energy band gap measured at room temperature was 3.61eV The energy band gap of zinc sulfide annealed in zinc vapor at $800^{\circ}C$ was lower 0.1eV than that of as-grown zinc sulfide through the analysis of the photocurrent spectra. The photoluminescence spectra were measured ranging from 30K to 293K for the two cases of as-grown and annealed zinc sulfide. As-grown ZnS single crystal had peaks at 350nm, 392nm, 465nm, and annealed zinc sulfide had peaks at 349nm.

• Journal of Life Science
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• v.23 no.4
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• pp.537-541
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• 2013

We analyzed glycerol using thin-layer chromatography (TLC) and compared the separation resolution of some mobile phases. When acetonitrile:distilled water (85:15 v/v) was used as a mobile phase, the band of glycerol on the TLC was more distinctly and rapidly separated. Using TLC analysis, we prepared a calibration curve for the glycerol concentration vs. the area of the glycerol band in which the glycerol concentration of the x-axis was converted into a log-scale ranging from 3.0 to 0.0625 (%, w/v). Based on this calibration curve, the residual glycerol concentration (0.2 [%, w/v]) in biodiesel was determined successfully using TLC analysis. When the results of the TLC analysis were compared with those of a chemical and enzymatic assay, the results were fairly similar. We conclude that TLC without additional analytical instruments can be used as an alternative method for the quantitative analysis of the concentration of glycerol in biodiesel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.125-130
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• 2011

In this paper, SIW-based $2{\times}4$ uniform array antenna with a sequentially fed 8-way power divider with an equal division characteristic is proposed for an application of X-band satellite communication. In particular, sequential feeding structures with a progressive phase difference of 90 degrees between the nearest elements have been suggested to protect the cancellation of electric fields due to the array alignments and to enhance the purity of RHCP(Right-Handed Circular Polarization). The obtained results according to the return loss bandwidth, RHCP antenna gain, axial ratio bandwidth are 760 MHz ranging from 7.90 to 8.66 GHz under the criterion of less than -10 dB, 14.3 dBic at 8.3 GHz, and 600 MHz from 8.15 to 8.75 GHz, respectively. In addition, it is observed that the equal-division characteristic of SIW-based 8-way power divider is approximately -9.2 dB in all ports.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.5
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• pp.179-186
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• 2007

Single crystal $CdGa_2Se_4$ layers were grown on a thoroughly etched semi-insulating GaAs(100) substrate at $420^{\circ}C$ with the hot wall epitaxy(HWE) system by evaporating the polycrystal source of $CdGa_2Se_4$ at $630^{\circ}C$. The crystalline structure of the single crystal thin films was investigated by the photoluminescence and double crystal X-ray diffraction(DCXD). The carrier density and mobility of single crystal $CdGa_2Se_4$ thin films measured with Hall effect by van der Pauw method are $8.27{\times}10^{17}cm^{-3},\;345cm^2/V{\cdot}s$ at 293 K, respectively. The photocurrent and the absorption spectra of $CdGa_2Se_4/SI$(Semi-Insulated) GaAs(100) are measured ranging from 293 K to 10 K. The temperature dependence of the energy band gap of the $CdGa_2Se_4$ obtained from the absorption spectra was well described by the Varshni's relation $E_g(T)=2.6400eV-(7.721{\times}10^{-4}eV/K)T^2/(T+399K)$. Using the photocurrent spectra and the Hopfield quasicubic model, the crystal field energy(${\Delta}cr$) and the spin-orbit splitting energy(${\Delta}so$) far the valence band of the $CdGa_2Se_4$ have been estimated to be 106.5 meV and 418.9 meV at 10 K, respectively. The three photocurrent peaks observed at 10 K are ascribed to the $A_{1^-},\;B_{1^-},\;and\;C_{11}-exciton$ peaks.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.304-308
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• 2003

A low cost solution employing harmonic oscillation to the frequency synthesizer at 5.8 GHz is proposed. The proposed frequency synthesizer is composed of 2.9GHz PLL chip, 2.9GHz oscillator, and 5.8GHz buffer amplifier. The measured data shows a frequency tuning range of 290MHz, ranging from 5.65 to 5.94GHz, about 0.5dBm of output power, and a phase noise of -107.67 dBc/Hz at the 100kHz offset frequency. All spurious signals including fundamental oscillation power (2.9GHz) are suppressed at least 15dBc than the desired second harmonic signal.

• IEMEK Journal of Embedded Systems and Applications
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• v.4 no.1
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• pp.29-34
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• 2009

In this paper, we design RF transceiver architecture and building blocks for impulse radio UWB system. Impulse radio UWB signal occupies the wide frequency band which is very low transmission power. So, it can minimize the interference effect with the other system. Using UWB technology, we obtain position awareness service. Therefore, we describe the RF transceiver architecture of direct conversion receiver and define the requirement of RF transceiver. Moreover, we implement a prototype RF transceiver based on the presented standard and verify a function and performance through the wireless data communication and ranging test.