• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.255-260
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• 2000

This paper presents a radio-telemetry patient monitor. which is used for intensive cal?e units. emergency and surgical operation rooms to monitor continuously patients' vital signs. The radio-telemetry patient monitor consists of a vital sign acquisition unit. wireless data transmission units and a vital sign-monitoring unit. The vital sign acquisition unit amplifies biological signals, performs analog signal to serial digital data conversion using the one chip micro-controller. The converted digital data is modulated FSK in UHF band using low output power and transmitted to a remote site in door. In comparison with analog modulation. FSK has major advantages to improve performance with respect to noise resistance with fower error and the potential ability to process and Improve quality of the received data. The vital sign-monitoring unit consists of the receiver to demodulate the modulated digital data, the LCD monitor to display vital signs continuously and the thermal head printer to record a signal.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.9 no.6
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• pp.539-545
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• 2016

In this paper, a novel coupled C type resonator is proposed for improvement of phase noise characteristics that is weak point of oscillator using planar type microstrip line resonator. Oscillator using proposed shorted coupled C type resonator is designed, it has improved phase noise characteristics. At the fundamental frequency of 9.8GHz, 4.87dBm output power and -84.7 dBc@100kHz phase noise have been measured for oscillator with shorted coupled C type resonator. Next, we designed voltage controlled oscillator using proposed shorted coupled C type resonator with varactor diode. The VCO has 33.8MHz tuning range from 9.7807GHz to 9.8145GHz, and phase noise characteristic is -115~-112.5dBc/Hz@100KHz. Due to its simple fabrication process and planar type, it is expected that the technique in this paper can be widely used for low phase noise oscillators for both MIC and MMIC applications.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9C
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• pp.1337-1344
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• 2004

This paper deals with analysis and real-time Implementation of a wide band adaptive multirate speech codec (AMR-WB) using a fixed-point DSP of TI's TMS320C6201. In the AMR-WB codec, input speech is divided into two frequency bands, lower and upper bands, and processed independently. The lower band signal is encoded based on the ACELP algorithm and the upper band signal is processed using the random excitation with a linear prediction synthesis filter. The implemented AMR-WB system used 218 kbytes of program memory and 92 kbytes of data memory. And its proper operation was confirmed by comparing a decoded speech signal sample-by-sample with that of PC-based simulation. Maximum required time of 5 75 ms for processing a frame of 20 ms of speech validates real-time operation of the Implemented system.

• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.263-267
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• 2009

Recently intrinsic and scattering quality factor ($\varrho_i^{-1}$ and $\varrho_s^{-1}$) was successfully separated from total quality factor ($\varrho_t^{-1}$) on the seismic data of the Korean Peninsula. From this result, we theoretically calculated the expected coda quality factor ($\varrho_{Cexp}^{-1}$) based on multiple scattering model, and compared with other quality factors such as $\varrho_t^{-1}$, $\varrho_i^{-1}$, $\varrho_s^{-1}$, and observed coda quality factor ($\varrho_c^{-1}$) obtained by single scattering model. While the $\varrho_{Cexp}^{-1}$ values are comparable to the $\varrho_i^{-1}$ values, the $\varrho_c^{-1}$ values are close to the values of $\varrho_t^{-1}$ rather than $\varrho_i^{-1}$ and $\varrho_{Cexp}^{-1}$ except for the 24 Hz frequency. This results suggest that the assumption of uniform scatterer in the Korean Peninsula is unrealistic.

• Geophysics and Geophysical Exploration
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• v.14 no.3
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• pp.249-253
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• 2011

Based on intrinsic and scattering quality factor ($Q_i^{-1}$ and$Q_s^{-1}$) obtained from the seismic data of the southeastern Korean Peninsula, the expected coda quality factor (${Q_{Cexp}}^{-1}$) was theoretically calculated using multiple scattering model, and was compared with other quality factors such as $Q_i^{-1}$, $Q_s^{-1}$, and observed $Q_C^{-1}$ obtained by single scattering model. While the ${Q_{Cexp}}^{-1}$ values are typically comparable to the $Q_i^{-1}$ values, the $Q_C^{-1}$ values are different from the ${Q_{Cexp}}^{-1}$ values except for the higher frequency. Future works require to consider depth-dependent attenuation.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.421-432
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• 2020

This paper proposes a 2-kW solid-state power amplifier (SSPA) developed by employing power amplifier pallets designed using gallium-nitride high electron mobility transistors, which is used in S-band military radars and to replace existing traveling-wave tube amplifier (TWTA). The SSPA consists of a high-power amplifier module, which combines eight power amplifier pallets, a drive amplifier module, a digital control module, and a power supply unit. First, the amplifier module and component were integrated into a small package to account for space limitations; next, an on-board harmonic filter was fabricated to reject spurious components; and finally, an auto gain control system was designed for various duty ratios because recent military radar systems are all active phase radars using the pulse operation mode. The developed SSPA exhibited a max gain of 48 dB and an output power ranging between 63-63.6 dBm at a frequency band of 3.1 to 3.5 GHz. The auto gain control function showed that the output power is regulated around 63 dBm despite the fluctuation of the input power from 15-20 dBm. Finally, reliability of the developed system was verified through a temperature environment test for nine hours at high (55 ℃) / low (-40℃) temperature profile in accordance with military standard 810. The developed SSPA show better performance such as light weight, high output, high gain, various safety function, low repair cost and short repair time than existing TWTA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3C
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• pp.271-280
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• 2008

M channel near-perfect-reconstruction(NPR) pseudo-QMF banks are a hybrid of conventional pseudo-QMF design and spectral factorization approach where the analysis and synthesis filters are cosine-modulated versions of the prototype-lowpass filter(p-LPF). However, p-LPF H(z) does not have linear-phase symmetry as well as magnitude-distortion optimization since it is obtained by spectral factorization of $2M^{-th}$ band filter $G(z)=z^{-(N-1)}H(z^{-1})H(z)$. A fair amount of attention, therefore, has been focused on the design of filter banks for reducing only alias-cancellation distortion without reconstructed-amplitude distortion. In this paper, we propose a new method for designing linear-phase p-LPF in NPR pseudo-QMF banks, which is based on Maxflat(maximally flat) FIR filters with closed-form transfer function. In addition, p-LPF H(z) is optimized in this approach so that the 2M-channel overall distortion response represented with $G(z)=H^2(z)$ approximately becomes an unit magnitude response. Through several examples of NPR pseudo-QMF banks, it is shown that the peek ripple of the overall magnitude distortion is less than $3.5{\times}10^{-4}\;({\simeq}-70dB)$ and analysis/synthesis filters have the sharp monotone-stopband attenuation exceeding 100 dB.

• Journal of the Korean Magnetics Society
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• v.19 no.6
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• pp.203-208
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• 2009

Magnetic and Ka-band absorbing properties have been investigated in Ti-Co substituted M-type barium hexaferrites with $BaTi_{0.5}Co_{0.5}Fe_{11}O_{19}$ composition. The ferrite powders were prepared by conventional ceramic processing technique and used as absorbent fillers in ferrite-rubber composites. The magnetic properties were measured by vibrating sample magnetometer. The complex permeability and dielectric constant were measured by using the WR-28 rectangular waveguide and network analyzer in the frequency range 26.5~40 GHz. For the Ti-Co substituted M-hexaferrites, the ferromagnetic resonance is observed at Ka-band (29.4 GHz). The matching frequency and matching thickness are determined by using the solution map of impedance matching. A wide band microwave absorbance is predicted with controlled ferrite volume fraction and absorber thickness.

• Korean Journal of Crystallography
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• v.3 no.2
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• pp.85-97
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• 1992

EBFZM( Electron Beam Floating Zone Melting) 법을 이용하여 몰리브덴에서의 금속계 불순물과 침입형 불순물의 정련기구 및 단결정 성장기구를 연구하 였다. Fe, Cr, Co등의 금속계 불순물은 몰리브덴과의 평형증기압의 차이에 따른 불순물의 선택적 증발에 의하여 우수한 정련효과를 나타내며, 몰리브덴보다 응점이 높은 Ta, W는 잘 제거되지 않았다. 한편 대역 정제에 의한 정련효과는 미약함을 확인하였다. EBF ZM은 C,0,N등의 침입형 불순물의 정련에도 효과적 이었다. 본 연구의 모든 조건에서 몰리브덴은 단결정으로 성장하였으며 2차 재결정 epitaxy에 의한 단결 정 성장기구가 제시되었다. 몰리브덴 단결정 내의 전 위밀도는 strain-anneal법에 의한 단결정의 경우보다 높았으며,본 실험의 열처리 조건에서는 변화하지 않았다. The purification and single crystal growth mechanisms of molybdenum were analysed in EBFZM ( electron beam floating zone melting). Metallic impurities of Fe, Cr, Co were purified efficiently but Ta and W were not removed well in this study. It was due to a preferential evaporation of the elements caused by the difference in equillibrium vapor pressure between the elements and molybdenum. The pu- rification effect by zone refining was not significant. The EBFZM also refined the interstitial impurities of C, 0 and N, effectively. The single crystals of molybdenum were grown regardless of the experimental conditions and the secondary recrystallization epitaxy was surge sled as a growth mechanism. The dislocation density in single crystal was higher than that by strain-anneal method, and was not reduced by heat treatments.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.12-24
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• 2001

The key advantage of LTCC(low temperature co-fired ceramics) technology is the ability to integrate passive components such as resistors, capacitors, and inductors. More compact circuits with an increased scale of integration are needed with the development for advanced telecommunication system such as IMT-2000. LTCC technology can be obtained by removing these elements from the substrate surface to inside of ceramic body. And it can miniaturize the wireless phone through integration of planar patch antenna, duplexer, band pass filter, bias line, circuit of impedance matching and RF choke etc. Futhermore, with the multilayer chip process and its outstanding electrical material characteristics, LTCC is predestined for highly-integrated, cost effective wide band applications. This paper focuses on the general description of LTCC MCM technologies and the fabrication of the multilayer VCO module.