• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.5 s.335
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• pp.61-68
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• 2005

In this paper, low conversion loss 94 GHz MIMIC resistive mixer was designed and fabricated. The $0.1{\mu}m$ InGaAs/InAlAs/GaAs Metamorphic HEMT, which is applicable to MIMIC's, was fabricated. The DC characteristics of MHEMT are 665 mA/mm of drain current density, 691 mS/mm of maximum transconductance. The current gain cut-off frequency(fT) is 189 GHz and the maximum oscillation frequency(fmax) is 334 GHz. A 94 GHz resistive mixer was fabricated using $0.1{\mu}m$ MHEMT MIMIC process. From the measurement, the conversion loss of the 94 GHz resistive mixer was 8.2 dB at an LO power of 10 dBm. P1 dB(1 dB compression point) of input and output were 9 dBm and 0 dBm, respectively. LO-RF isolations of resistive mixer was obtained 15.6 dB at 94.03 GHz. We obtained in this study a lower conversion loss compared to some other resistive mixers in W-band frequencies.

• Proceedings of the IEEK Conference
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• 2004.06b
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• pp.339-342
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• 2004

본 논문은 밀리미터파 대역 무선통신 시스템 송신부의 응용을 위해 CPW 구조를 이용하여 V-band용 상향 주파수 혼합기와 2단 구동증폭기를 설계$\cdot$제작하였다. 능동소자는 본 연구실에서 제작한 $0.1{\mu}m$ 게이트 GaAs Pseudomorphic HEMTs(PHEMTs)를 사용하였으며 입$\cdot$출력단은 CPW를 사용해 정합 회로를 설계하였다. 제작된 상향 주파수 혼합기는 LO power 5.4 dBm, 2.4 GHz IF 신호를 -10.25 dBm으로 입력하였을 때 Conversion Loss 1.25 dB, LO-to-RF Isolation은 58 GHz에서 13.2 dB의 특성을 나타내었다 2단 구동 증폭기는 측정결과 60 GHz에서 S21 이득 13 dB, $58\;GHz\;\~\;64\;GHz$ 대역에서 S21 이득 12 dB 이상을 유지하는 광대역 특성을 얻었고 증폭기의 Pl dB는 3.8 dBm, 최대 출력전력은 6.5 dBm의 특성을 얻었다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.67-74
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• 2005

In this paper, high LO-RF isolation W-band MIMIC single-balanced mixer was designed and fabricated using a branch line coupler and a $\lambda$/4 transmission line. The simulation results of the designed 94 GHz balun show return loss of -27.9 dB, coupling of -4.26 dB, and thru of -3.77 dB at 94 GHz, respectively. The isolation and phase difference were 23.5 dB and $180.2^{\circ}$ at 94 GHz. The W-band MIMIC single-balanced mixer was designed using the 0.1 $\mu$m InGaAs/InAlAs/GaAs Metamorphic HEMT diode. The fabricated MHEMT was obtained the cut-off frequency(fT) of 189 GHz and the maximum oscillation frequency(fmax) of 334 GHz. The designed MIMIC single-balanced mixer was fabricated using 0.1 $\mu$m MHEMT MIMIC Process. From the measurement, the conversion loss of the single-balanced mixer was 23.1 dB at an LO power of 10 dBm. Pl dB(1 dB compression point) of input and output were 10 dBm and -13.9 dBm respectively. The LO-RF isolations of single-balanced mixer was obtained 45.5 dB at 94.19 GHz. We obtained in this study a higher LO-RF isolation compared to some other balanced mixers in millimeter-wave frequencies.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.575-578
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• 2005

We report on a low-cost V-band wireless transceiver with no use of any local oscillator in the receiver block using a self-heterodyne architecture. V-band Microwave monolithic IC (MMIC) modules were developed to demonstrate the wireless transceiver using coplanar waveguide (CPW) and GaAs PHEMT technologies. The MMIC modules such as the MMIC low noise amplifier (LNA), medium power amplifier (MPA) and the up/down-mixer were installed in the transceiver system. To interface the MMIC chips with the component modules for the transceiver system, CPW-to-waveguide fin-line transition modules of WR-15 type were designed and fabricated. The fabricated LNA modules showed a $S_{21}$ gain of 8.4 dB and a noise figure of 5.6 dB at 58 GHz. The MPA modules exhibited a gain of 6.9 dB and a $P_1$ $_{dB}$ of 5.4 dBm at 58 GHz. The conversion losses of the up-mixer and the down-mixer module were 14.3 dB at a LO power of 15 dBm, and 19.7 dB at a LO power of 0 dBm, respectively. From the measurement of V-band wireless transceiver, a conversion gain of 0.2 dB and a P $_{1dB}$ of 5.2 dBm were obtained in the transmitter block. The receiver block showed a conversion gain of 2.1 dB and a P $_{1dB}$ of -18.6 dBm. The wireless transceiver system demonstrated a successful data transfer within a distance of 5 meters.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.7
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• pp.992-1000
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• 1998

In the present study the behavior of laminar-wavy film flowing down a vertical plate was studied analytically. The effects of film Reynolds number and interfacial shear stress on the mean film thickness, wave amplitude, wave length, and wave celerity were analysed. The anayltical results on the periodic-wave falling film showed good agreements with experimental data for Re < 100. As the film Reynolds number increased, mean film thickness, wave amplitude, and wave celerity increased, but wave length decreased. Depending on the direction of interfacial shear stress, the shape of wavy interface was disturbed significantly, especially for the intermediate-wave. As the interfacial shear stress increased, for the periodic-wave film, wave amplitude and wave celerity increased, but mean film thickness and wave length decreased.

• ETRI Journal
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• v.33 no.3
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• pp.462-465
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• 2011

A millimeter-wave (mm-wave) high-linear low-noise amplifier (LNA) is presented using a 0.18 ${\mu}m$ standard CMOS process. To improve the linearity of mm-wave LNAs, we adopted the multiple-gate transistor (MGTR) topology used in the low frequency range. By using an MGTR having a different gate-source bias at the last stage of LNAs, third-order input intercept point (IIP3) and 1-dB gain compression point ($P_{1dB}$) increase by 4.85 dBm and 4 dBm, respectively, without noise figure (NF) degradation. At 33 GHz, the proposed LNAs represent 9.5 dB gain, 7.13 dB NF, and 6.25 dBm IIP3.

• Journal of Photoscience
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• v.7 no.4
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• pp.161-167
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• 2000

Temperature-dependent electroretinogram responses were investigated in the dark adapted bullfrog eyes within the physiological temperature range 0-40$\^{C}$. In hypothermic process(25→0→25$\^{C}$), the amplitude of b-and c-wave decreased with lowering the temperature again. Both b-wave amplitude and threshold responses were maximal around 15$\^{C}$ during the temperature increment. Upon warming to room temperature again (25$\^{C}$), the b-wave amplitude was approximately doubled as compared to that of control without temperature changes. During the hyperthermic process (25→40→25$\^{C}$), however, the responses decreased with warming, and the wave amplitude failed to recover by cooling to 25$\^{C}$ again. As describe above, the recoveries of ERG in both processes show the striking difference. The hypothermia induces the amplification of the b-wave, that is, enhances the retinal function with the temperature recovery toward room temperature. While the hypertherima produces the decrease of the b-wave even though recovered to room temperature, which indicates an irreversible retina. The morphological alteration is shown both hypothermic and hyperthermic process, such as an appearance of large vacuoles and degenerating outer segments, more intense in hyperthermia, similar to light induced damage.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.74-79
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• 2010

We have designed a millimeter-wave passive imaging sensor with multi-horn antenna array. Six horn array antenna is suggested that it is integrated into one housing, and this antenna is effectively configurated m space to assemble with LNA of WR-10 structure. Antenna is designed to have the peak gain of 17.5dBi at the center frequency of 94GHz, and the return loss of less than -25dB in W-band, and the small aperture size of $6mm{\times}9mm$ for antenna configuration with high resolution. LNA is designed to have total gain of more than 55dB and noise figure of less than 5dB for good sensitivity. We made a detector for DC output translation of millimeter-wave signal with zero bias Schottky diode. It is shown that good sensitivity of more than 500mV/mW.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.842-847
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• 2005

In this paper, we fabricated sheet-type EM wave absorbers for mobile phones by using sendusts and tested EM wave absorption of it. The band-width of EM wave absorbers coated with $Al_2O_3$ were larger than non-coated EM wave absorbers. Particle size decreased with increasing milling time, which made the result of increasing of EM wave absorption. The fabricated EM wave absorbers show a reflection coefficient 17.4 dB at 946 MHz for a 4 mm sample and 5 dB at 1.8 GHz for a 1 mm sample.

• Journal of Navigation and Port Research
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• v.30 no.8 s.114
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• pp.637-642
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• 2006

In this paper, we made an experiment on materials of two kinds. First, we made a study of Multi-layer EM wave absorbers using Sendust. In result, The bandwidth of the Multi-layer Sendust EM wave absorbers over 10 dB is extended in S-Band. Second, we investigated the mixing effects of AI(OH)3 on Multi-layer Sendust EM wave Absorbers. In result, the Multi-layer Sendust EM wave absorbers mixed with Al(OH)3 showed a extended bandwidth over 10 dB compared with non-mixed Multi-layer Sendust EM wave absorbers in S-Band.