• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.5
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• pp.574-581
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• 2016

Trend on high-power GaN(Gallium Nitride) SSPA(Solid-State Power Amplifier) and its availability in miniature radar systems are presented. There are numerous studies on high-power GaN devices since they have some characteristics of high-breakdown voltage, high power density, and high-temperature stability. Recent scaled GaN technology makes it possible to apply it in SSPAs for W- and G-band applications, with increasing its maximum frequency. In addition, it leads to downsizing and power-efficiency improvement of SSPAs, which means that GaN SSPAs can be available in miniature radar systems. This study also shows radar performance and comparison in the case of using such SSPAs at three frequency bands of Ku, Ka, and W. Finally, we demonstrate prospects of scaled GaN SSPAs in future miniature radar systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.515-517
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• 2016

In this paper, we develope a stretchable wearable device containing services for processing physiological signals to extract emotion information. The emotion extracting algorithm conducts to recognize emotion from EDR, SKT, and HRV signals measured with the fabric sensors. In addition, the suggested wearable device can also solve the problems faced with today's many other wearable devices: 1) limited battery life 2) the lack of compatibility and expandability due to run on internal components designed for smart phone 3) the design has always been a crucial factor in determining the success of main stream consumer wearable devices.

• Transactions on Electrical and Electronic Materials
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• v.3 no.1
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• pp.18-22
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• 2002

ITO thin films with thickness of 3000 $\AA$ were fabricated by rf magnetron sputtering system with a 10 mol % SnO$_2$-90 mol % In$_2$O$_3$target at various substrate temperature and annealing temperature in air. And we investigated structural, electrical and optical characteristics of them. It's resistivity, carrier concentration and Hall mobility was 2$\times$10$\^$-4/ Ωcm, 7$\times$10$\^$20/∼ 9$\times$10$\^$20/ cm$\^$-3/ and 21∼23 cm$^2$/V$.$sec respectively. And it's optical transmittance and energy band gap was above 85 % in the visible range and 3.53 eV respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.89-96
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• 2000

In this paper, the design theory of the corrugated polarizer using square waveguide is proposed. In order to analysis the characteristic of square waveguide discontinuity as well as achievement of the low VSWR, we apply the modified $TE^\chi_mn$ mode matching method and the corrugated exponential function to the polarizer design. The results show a broadband characteristic that phase shift angle is nearly appeared $90^{\circ}$ in the range of 11.7-15.8GHz. Especially, we could be designed the Ku-band dual polarizer for the satellite broadcasting transponder with 300MHz bandwidth. Its phase shift angle and maximum VSWR, axial ratio are $90^{\circ},\pm1^{\circ}$, 1.03, and 1.0001 in the range of 11.7-12.0GHz and 14.5-14.8GHz, respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.657-664
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• 2011

This paper shows a whole noise quality checking system for the new developed 6th speed automatic transmission manufactured in USA. Due to demand for manufacturing of the high NVH quality transmissions in the mass product line, some special checking system called EOL NVH is adapted. This EOL system is using vibration sensor and analysis technologies. Through adapting vibration analysis technologies and functions likewise RMS, crest factor, harmonics, peak, band and order tracking, various noise problems caused by wear, nick and deformations could be successfully detected and predicted. Therefore, automatic transmissions manufactured in the USA could get high NVH quality. The developing process described in this paper and results on EOL system will offer good guides to the engineers who built the next transmission factory.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.159-160
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• 2014

In this paper, a design method for a broadband planar dipole antenna for the terrestrial digital television (DTV) reception is studied. The proposed antenna is an asymmetrical planar dipole consists of a rectangular patch with an embedded t-shaped slit, and the antenna shape is printed on a side of an FR4 substrate. The effects of geometrical parameters on the antenna performance are examined, and the parameters are adjusted to operate in the DTV frequency band of 470-806 MHz. The prototype antenna is fabricated on an FR4 substrate with a size of $260mm{\times}30mm$. The performance of the antenna is tested experimentally to verify the results of this study.

• International Journal of Computer Science & Network Security
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• v.22 no.3
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• pp.382-388
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• 2022

Satellite communication for high altitude platform stations (HAPS) and low earth orbit (LEO) systems suffer from dust and sand (DU&SA) storms in the desert regions such as Saudi Arabia. These attenuations have a distorting effect on signal fidelity at high frequency of operations. This results signal to noise ratio (SNR) to dramatically decreasing and leads to wireless transmission error. The main focus in this paper is to propose common relations between HAPS and LEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three dimensional relationship for HAPS and LEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gaseous effects for different frequency, and propagation angle to provide system operations with a predicted vision of satellite parameters' values. Skillful decision and control system (SD&CS) is proposed to control applied parameters that lead to improve satellite network performance and to get the ultimate receiving wireless signal under bad weather condition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.4
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• pp.7-11
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• 2006

In this paper, it is reported that film-bulk-acoustic resonator with high c-axis oriented AIN film on $Mo/SiO_2/Si(100)$ using metal-organic-chemical-vapor deposition was fabricated. The resonant frequency and anti-resonant frequency of the fabricated resonator were observed with 3.189[GHz] and 3.224[GHz], respectively. The quality factor and the effective electromechanical coupling coefficient(${k_{eff}}^2$) were measured with 24.7 and 2.65[%], respectively. The conditions of AIN deposition were substrate temperature of $950[^{\circ}C]$, pressure of 20Torr, and V-III ratio of 25000. A high c-axis oriented AIN film with $4{\times}10^{-5}[\Omega{cm}]$ resistivity of Mo bottom electrode and $4[^{\circ}]$ of AIN(0002) full-width at half-maximum(FWHM) on $Mo/SiO_2/Si(100)$ was grown successfully. The FWHM value of deposited AIN film is useful for the RF band pass filter specification for GHz-band wireless local area network.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.8
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• pp.664-669
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• 2012

Nano-structured one-dimensional $Na_2Ti_6O_{13}$ particles were synthesized by a molten salt process. Effects of processing parameters on the microstructure and band gap energy of the $Na_2Ti_6O_{13}$ powder were studied in this paper. For the synthesis of the $Na_2Ti_6O_{13}$ particles, two different raw materials of tubular shaped Na-titanate (Na-TiNT) and spherical shaped $TiO_2$ were utilized. Synthesizing with the raw material of Na-TiNT, around 70nm thick 1D-$Na_2Ti_6O_{13}$ with the bandgap energy of 3.5 eV was obtained at $810^{\circ}C$. Below $810^{\circ}C$ or without the presence of NaCl, 1D-$Na_2Ti_6O_{13}$ was in a relatively short in length and agglomerated state. With the processing temperature increased, the thickness of the 1D-$Na_2Ti_6O_{13}$ was also observed to be increased. On the other hand, when $TiO_2$ was employed as a raw material, the mixed amount of $Na_2CO_3$ played an important role in transforming the morphology and phase of the raw material, affecting the bandgap energy of the synthesized product. Specific surface area of the synthesized 1D-$Na_2Ti_6O_{13}$ was significantly affected by the raw and mixed materials as well as processing temperature. When Na-TiNT was processed at $810^{\circ}C$ with NaCl, the specific surface area of the 1D-$Na_2Ti_6O_{13}$ showed the best value of 30.63 $m^2/g$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1339-1349
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• 2008

In this paper, a nonlinear relationship between an input complex envelope and an output complex envelope of m-th harmonic zone is theoretically analyzed, and AM/$AM_m$ and AM/$PM_m$ are defined. A scheme to extract these characteristics from measured in-phase and quadrature-phase data is suggested. The proposed analysis is verified with a fundamental-fundamental and fundamental-third harmonic measurements for a InGaP power amplifier(PA). Based on the harmonic-band nonlinear analysis and extraction scheme, a new technique to send a signal in m-th harmonic band with a harmonic signal Linearization Digital Predistortion(DPD) scheme is presented. A numerical analysis and a Look-Up Table(LUT) based DPD algorithms to linearize output signal on m-th harmonic zone are developed. For a 16- and a 64-QAM input signals, a DPD for third harmonic signal linearization is implemented, and output spectrum and signal constellation are measured. The wholly distorted signals are linearized, and thus the measured Error Vector Magnitudes (EVM) are 6.4 % and 6.5 % respectively. The results show that a proposed scheme linearizes a nonlinearly distorted harmonic band signals. The proposed nonlinear analysis and predistortion scheme can be applied to multiband transmitter in next generation software defined radio(SDR)/cognitive radio(CR) wireless system.