• Journal of the Microelectronics and Packaging Society
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• v.9 no.3
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• pp.19-23
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• 2002

This paper presents a micro fluxgate magnetic sensor in printed circuit board (PCB). In order to observe the effect of the closed magnetic path, the magnetic cores of rectangular-ring and two bars were each fabricated. Each fluxgate sensor consists of five PCB stack layers including one layer magnetic core and four layers of excitation and pick-up coils. The center layer as a magnetic core is made of a Co-based amorphous magnetic ribbon with extremely high DC permeability of ~100,000. Four outer layers as an excitation and pick-up coils have a planar solenoid and are made of copper foil. In case of the fluxgate sensor having the rectangular-ring shaped core, excellent linear response over the range of -100 $\mu$T to ＋ 100 $\mu$T is obtained with 540 V/Tsensitivity at excitation square wave of 3 $V_{p-p}$ and 360 KHz. The chip size of the fabricated sensing element is $7.3 \times 5.7\textrm{mm}^2$. The very low power consumption of ~8 mW was measured. This magnetic sensor is very useful for various applications such as: portable navigation systems, telematics, VR game and so on.n.

• Journal of the Korean Vacuum Society
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• v.9 no.2
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• pp.136-143
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• 2000

$SrBi_2Ta_2O_9;(SBT)$ films were deposited on p-type Si(100) at room temperature by rf magnetron sputtering method to confirm the possibility of application of $Pt/SBT/Pt/Ti/SiO_2/Si$ structure (MFM) for destructive read out ferroelectric RAM (random access memory). Their structural characteristics with the various annealing times and Ar/$O_2$ gas flow ratios in sputtering were observed by XRD (X-ray diffractometer) and the surface morphologies were observed by FE-SEM (field emission scanning electron microscopy), and their electrical properties were observed by P-V (polarization-voltage measurement) and I-V (current-voltage measurement). The Ar/$O_2$ gas flow ratios of sputtering gas were changed from 1 : 4 to 4 : 1 and SBT thin films were deposited at room temperature. The films show (105), (110) peaks of SBT by XRD measurement. SBT thin films deposited at room temperature were crystallized by furnace annealing at 80$0^{\circ}C$ in oxygen atmosphere during either one hour or two hours. Among their electrical properties, P-V curves showed shaped hysteresis curves, but the SBT thin films showed the asymmetric ferroelectric properties in P-V curves. When Ar/$O_2$ gas flow ratios are 1 : 1, 2: 1, the leakage current density values of SBT thin films are good, those values of 3 V, 5 V, and 7 V are respectively $3.11\times10^{-8} \textrm{A/cm}^2$, $5\times10^{-8}\textrm{A/cm}^2$, $7\times10^{-8}\textrm{A/cm}^2$.After two hours of annealing time, their electrical properties and crystallization are improved.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.4
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• pp.92-100
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• 1985

New N+N/P HLE solar cells with N+ surface charge accumulated layer in the emitter region are fabricated on the N/P Si epiwafer by incorporating high fixed positive charge density (Qss) at the Si-AR layer interface. Solar cells are classified into two categories, i.e, OCI and NCI Cell depending on AR layer, SiOl and Si3 N4/sioxynitride layer respectively. The distribution of Qss in the Si-AR layer interface is examined by C-V plot. It shows that the surface charge accumulated layer is formed more effectively in the NCI cell (Qss=1.79-1.84$\times$1012cm-2) than in the OCI cell (Qss=3.03~4.40$\times$1011 cm-2). The efficiency characteristics are evaluated under the JCR halogen lamp of 100 mw/cm2. The average (maximum) conversion efficiency for active area is 15.18 (15.46)% in the OCI cell and 16.31 (17.07)% in the NCI cell.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.5
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• pp.337-343
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• 2013

In this paper, IEEE 802.11 based WLAN(5.2/5.8GHz) wideband Weathercock-shaped microstrip patch antenna was designed and manufactured. The antenna has a size of $17.4{\times}17.4mm^2$ and utilized FR-4 board. The size was minimized for mobility, and Weathercock-shaped U-slot and short-pin was inserted to satisfy adequate bandwidth and double bandwidth resonance characteristics. In addition, the antenna incorporated single both-sided patch, and simulation design optimized the Weathercock-shaped, position of the U-slot and the short-pin, and the length of the patch for the measurement. The manufactured antenna achieved a bandwidth of 695MHz from 5.2~5.8GHz zone(Return loss<-10dB). Achieved a beam width of $81.13^{\circ}$ and $85.43^{\circ}$ for 3-dB beam width of H plane and E p;ane radiation pattern, there was 3.17~4.85dBi gain.

• Solar Energy
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• v.10 no.3
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• pp.60-65
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• 1990

[ $n^+-p^+$ ] InP homojunction solar cells were fabricated by thermal diffusion of sulphur into a $p^+$-InP wafer($p=4{\times}10^{18}cm^{-3}$), and a SiO film($600{\AA}$ thick) was coated on the $n^+$ layer as an antireflection(AR) coating by an e-beam evaporator. The volume of the cells were $5{\times}5{\times}0.3mm^3$. The front contact grids of the cells with 16 finger pattern of which width and space were $20{\mu}m$ and $300{\mu}m$ respectively, were formed by photo-lithography technique. The junction depth of sulphur were as shallow as about 0.4r m We found out the fabricated solar cells that, with increasing the diffusion time, short circuit current densities($J_{sc}$), series resistances($R_s$) and energy conversion efficiencies(${\eta}$) were increased. The cells show good spectral responses in the region of $5,000-9,000{\AA}$. The short circuit current density, the open circuit voltage( $V_{oc}$), the fill factor(F.F) and the energy conversion efficiency of the cell were $13.16mA/cm^2$, 0.38V, 53.74% and 10.1% respectively.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.1
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• pp.19-25
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• 2008

In this paper, the front end module (FEM) was proposed for 2.4GHz WLAN band by LTCC multilayer application. The FEM was composed of power amplifier IC, switch IC, and LTCC module. LTCC module consists of output matching circuit and lowpass filter as Tx part, bandpass filter as Rx part. Design of output matching circuit for LTCC was used matching parameter from output matching circuit based on lumped circuit on the PCB board. The dielectric constant of LTCC substrate is 9. The substrate was composed of total 26 layers with each 30um thickness. Ag paste was used for the internal pattern as the conductor material. The size of the module is $4.5mm{\times}3.2mm{\times}1.4mm$. The fabricated FEM showed the gain of 21dB, ACPR of less than -31dBc first side lobe and Less than -59dBc second side lobe and the output power of 23Bm at P1dB.

• Journal of Sensor Science and Technology
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• v.12 no.2
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• pp.72-78
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• 2003

To observe the effect of excitation coil pitch on the micro fluxgate magnetic sensor, two sensors are fabricated using multi layer board process and the pitch distance of excitation coil are $260\;{\mu}m$ and $520\;{\mu}m$, respectively. The fluxgate sensor consists of five PCB stack layers including one layer of magnetic core and four layers of excitation and pick-up coils. The center layer as magnetic core is made of a Co-based amorphous magnetic ribbon with extremely high DC permeability of ${\sim}100,000$ and has a rectangular-ring shape to minimize the magnetic flux leakage. Four outer layers as excitation and pick-up coils have a planar solenoid structure and are made of copper foil. In case of the fluxgate sensor having the excitation coil pitch of $260\;{\mu}m$, excellent linear response over the range of $-100\;{\mu}T$ to $+100\;{\mu}T$ is obtained with sensitivity of 780 V/T at excitation sine wave of $3V_{p_p}$ and 360 kHz. The chip size of the fabricated sensing element is $7.3\;{\times}\;5.7\;mm^2$. The very low power consumption of ${\sim}8\;mW$ is measured. This magnetic sensor is very useful for various applications such as: portable navigation systems, telematics, VR game and so on.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.11A
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• pp.902-911
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• 2003

Using InGaP/GaAs HBT power cells with a 2.0${\times}$20$\mu\textrm{m}$$^2$ emitter area of a unit HBT, a two stage MMIC power amplifier has been developed for IMT-2000 handsets. An active-bias circuit has been used for temperature compensation and reduction in the idling current. Fitting on measured S-parameters of the HBT cells, circuit elements of HBT's nonlinear equivalent model have been extracted. The matching circuits have been designed basically with the extracted model. A two stage HBT MMIC power amplifier fabricated using ETRI's HBT process. The power amplifier produces an 1-㏈ compressed output power(P$\_$l-㏈/) of 28.4 ㏈m with 31% power added efficiency(PAE) and 23-㏈ power gain at 1.95 GHz in on-wafer measurement. Also, the power amplifier produces a 26 ㏈m output power, 28% PAE and a 22.3-㏈ power gain with a -40 ㏈c ACPR at a 3.84 ㎒ off-center frequency in COB measurement.quency in COB measurement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.238-246
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• 2004

This paper reports an experimental study around a module about forced air flow by blower (35${\times}$35${\times}$6㎣) in a portable personal computer model(200${\times}$235${\times}$10㎣). Experimental report is to know three data to investigate thermal resistance, adiabatic wall temperature and visualized fluid flow around the module by combination of the moving number and the arrangement method of blower. The channel inlet flow velocity has been varied between 0.26, 0.52 and 0.78㎧, and input power ( $Q_{p}$) to the module is 4W. To investigate thermal resistance. the heated module is mounted on two boards(110${\times}$110${\times}$1.2㎣, k=20.73, 0.494W/ $m^{\circ}C$) in parallel-plate channel to forced air flow. The temperature distribution were visualized by heated module on acrylic board(k=0.262W/ $m^{\circ}C$) using liquid crystal film. Fluid flow around the module were visualized using particle image velocimetry system.

• Journal of the Korean Vacuum Society
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• v.1 no.3
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• pp.360-370
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• 1992

HWE(Hot-Wall Epitaxy) 방법에 의하여 pyrex 유리기판 위에 CdS 다결정 박막을 성장하였다. X-선 회절실험 결과 CdS 박막은 육방정이었는데 (0002)면보다 91013)면이 강 하게 성장됨을 알 수 있었다. 전자현미경으로 표면을 분석한 결과 입자의 크기는 기판의 온 도가 48$0^{\circ}C$, 증발원의 온도가 $610^{\circ}C$일 때 1~1.5$mu extrm{m}$로서 가장 컸다. 박막의 표면저항은 4-point probe로서 측정한 결과 10-8$\Omega$/\ulcorner이상이었다. 성장된 CdS 다결정 박막의 photoluminesence을 20K에서 측정하였는데 bound exciton, donor acceptor pair에 의한 발광이 관측되었다. Spectral response의 peak는 505nm이었다. CdS 다결정 박막의 표면 저항을 줄이기 위하여 여러 가지 온도에서 Indium을 확산시켰다. 그 결과 표면저항은 ~ $\times$ 101에서 ~ $\times$ 103$\Omega$/\ulcorner 정도 감소되었다. 50$0^{\circ}C$에 In을 1시간 확산시켰을 때 표면저항은 1300$\Omega$/\ulcorner이었다. 이 때 CdS : In의 운반자 농도는 1.2 $\times$ 1018cm-3, 이동도는 1.8cm-2/V-sec, 비저항은 1.3 $\times$ 10-2$\Omega$-cm이었다. CdS : In의 photoluminescence는 20K 에서 Gaussian curve를 보여 주었으며 peak의 위치는 510nm이었다. CdS : In 박막의 spectral response의 peak는 상온에서 500nm이다. CdS : In 광전도 cell의 sensitivity ${\gamma}$ =0.77이고, 최대 허용소비전력은 p=120mW, 100lux에서 rise time은 8 msec, decay time 은 6 msec이다.