• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2001년도 종합학술발표회 논문집 Vol.11 No.1
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• pp.209-212
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• 2001

본 논문에서는 Ka-band 위성 중계기용 국부 발진기에 사용하게 될 전압제어 발진기의 EM (Engineering Model)을 비선형 방법으로 설계하였다. 전압제어 발진기의 위상잡음을 개선하기 위하여 공진기로 사용되는 유전체 공진기와 결합하는 마이크로스트립 라인을 high impedance inverter로 구현함으로써 공진회로의 quality factor를 우수하게 유지하여 능동소자에 전달되도록 하였다. 개발된 전압제어 발진기는 0～12V의 제어전압으로 9.7965～9.8032GHz의 발진범위를 갖으며 공급전력은 8V, 17mA을 필요로 한다. 제작된 전압제어 발진기의 위상잡음은 -96.51dB/Hz @10KHz와 -116.5dBc/Hz @100KHz의 특성을 나타내며 출력전력은 7.33dBm을 얻었다.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.997-1001
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• 2014

In this paper, the interference in small MIMO antennas having two identical composite right- and left-handed transmission-line(CRLH-TL)-based radiating elements is remarkably decreased. The radiating element has the broadside-capacitive coupling as well as slots to be equivalent to the CRLH-TL to prevent the size from increasing for an LTE high band. The suspended line bridging the two radiating elements is optimized to lower the interference between them down to -23 dB, while the overall MIMO antenna system is compact and its antenna performance is acceptable. The design is tested for 2.5 GHz.

• 전기전자학회논문지
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• 제22권4호
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• pp.1088-1092
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• 2018

In this paper, we propose a dual-mode frequency tripler using push-push and stacked FET structures. The proposed circuit can operate either in frequency multiplier mode or in amplifier mode. In the frequency multiplier mode, push-push frequency multiplication is achieved by allowing input signals with particular phase shifts. In the amplifier mode, the device operates as a distributed amplifier to obtain high gain. Also both modes were designed using stacked FET structure. The designed circuit showed frequency tripled output power of 9.7 dBm at 2.4 GHz with the input at 800 MHz. On the other hand, in the amplifier mode, the device showed 8.9 dB of gain to generate 19.5 dBm at 800 MHz.

• Current Optics and Photonics
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• 제7권4호
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• pp.378-386
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• 2023

A wideband instantaneous frequency measurement (IFM) system is been proposed, designed and analyzed. Phase modulation to intensity modulation conversion is implemented based on the stimulated Brillouin scattering (SBS) effect, and the microwave frequency can be measured by detecting the change in output power. Theoretical analysis shows that the frequency measurement range can be extended to 4f_b by adjusting the two sweeping signals of the phase modulators with a difference of 2f_b. The IFM system is set up using VPI transmission maker software and the performances are simulated and analyzed. The simulation results show that the measurement range is 0.5-45.96 GHz with a maximum measurement error of less than 9.9 MHz. The proposed IFM system has a wider measurement range than the existing SBS-based IFM system.

• 한국정보기술학회 영문논문지
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• 제9권1호
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• pp.11-24
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• 2019

This paper investigates the performance comparison of a Terahertz (THz) communications for a single-carrier and a multi-carrier single antenna point-to-point communication system. The multi-carrier system and single carrier system consider the orthogonal frequency division multiplexing (OFDM) and the minimum mean square error linear equalizer (MMSE-LE), respectively. We compare the frame-error-rate (FER) and throughput performance of both the systems for a THz communication environment with the carrier frequency of 300GHz and the tapped delay line (TDL) channel models described in 3GPP. It is observed from the simulation results that the OFDM systems outperform the MMSE-LE for various configurations.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 영호남학술대회 논문집
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• pp.78-81
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• 2000

A new type low-pass filter design method based on a coupled line and transmission line theory is proposed to suppress harmonics by attenuation poles in the stop band The design formula are derived using the equivalent circuit of a coupled transmission line. The new low-pass filter structure is shown to have attractive properties such as compact size, wide stop band range and low insertion loss. The seventh-order low-pass filter designed by present method Ins a cutoff frequency of 0.9 GHz with a 0.01 dB ripple level. The coupled line type low-pass filter with stripline configuration was fabricated by using a high-temperature superconducting (HTS ; $YBa_2Cu_3O_{7-x}$) thin film on MgO(100) substrate. Since the HTS coupled line type low-pass filter was proposed with five attenuation poles in stop band such as 1.8, 2.5, 4, 5.5, 62 GHz. The fabricated low-pass filter has improved the attenuation characteristics up to seven times of the cutoff frequency Bemuse of good rejection of the spurious signals and harmonics, our low-pass filter is applicable to mobile base station systems such as cellular, personal communication systems and international mobile telecommunication(IMT)-2000 systems.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
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• pp.301-304
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• 2008

Since longer wavelength microwave radiation can penetrate clouds, satellite passive microwave sensors can observe sea ice of the entire polar region on a daily basis. Thus, it is becoming popular to derive sea ice motion vectors from a pair of satellite passive microwave sensor images observed at one or few day interval. Usually, the accuracies of derived vectors are validated by comparing with the position data of drifting buoys. However, the number of buoys for validation is always quite limited compared to a large number of vectors derived from satellite images. In this study, the sea ice motion vectors automatically derived from pairs of AMSR-E 89GHz images (IFOV = 3.5 ${\times}$ 5.9km) by an image-to-image cross correlation were validated by comparing with sea ice motion vectors manually derived from pairs of cloudless MODIS images (IFOV=250 ${\times}$ 250m). Since AMSR-E and MODIS are both on the same Aqua satellite of NASA, the observation time of both sensors are the same. The relative errors of AMSR-E vectors against MODIS vectors were calculated. The accuracy validation has been conducted for 5 scenes. If we accept relative error of less than 30% as correct vectors, 75% to 92% of AMSR-E vectors derived from one scene were correct. On the other hand, the percentage of correct sea ice vectors derived from a pair of SSM/I 85GHz images (IFOV = 15 ${\times}$ 13km) observed nearly simultaneously with one of the AMSR-E images was 46%. The difference of the accuracy between AMSR-E and SSM/I is reflecting the difference of IFOV. The accuracies of H and V polarization were different from scene to scene, which may reflect the difference of sea ice distributions and their snow cover of each scene.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.197-201
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• 2001

The microwave dielectric properties of (1-x)Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3)O$_3$(x=0.25~0.5) ceramics depending on the Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BCN] contents and the possibility of application as a microwave dielectric resonator were investigated. The specimens were prepared by he conventional mixed oxide method using there sintering temperature of 1575$^{\circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As the mole fraction of BCN increased, dielectric constant increased while temperature coefficient of resonant frequency decreased. The highest value of quality factor, Qxf$_{0}$=138,205GHz, obtained in the sample of 0.9BMT-0.1BCN ceramics. In the range of x$\geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Qxf$_{0}$=75,325GHz and $\tau$$_{f}$=2.9015ppm/$^{\circ}C$.EX>.EX>.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.110-115
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• 2010

최근 도심지의 지하철 노선들은 과거에 지어진 지하철 노선들에 비하여 대심도 터널이 증대하고 있다. 신금호 역사(5호선, 깊이 : 46m)는 수도권에 있는 지하철 역사 중에서 3번째로 깊은 역사로서 대심도 역사의 모델로 선정되었으며, 신금호 전체 역사에 대한 화재시뮬레이션을 시도하였다. 신금호 역사는 3개의 출입구, 지하 1층 대합실, 지하 2층 대합실, 지하 2층에서 8층으로의 연결통로, 지하 8층 승강장으로 구성되어 있다. 본 연구에서는 지하 8층 승강장에서 지상 출입구 까지 전체 역사를 대상으로 연기거동을 해석하기 위하여 9,000,000개의 격자를 생성하였으며, 계산 효율을 증대시키기 위하여 19개의 블록으로 나누어서 처리하였다. 화재해석은 화재에 특화된 CFD 코드인 FDS를 사용하였으며 난류해석 기법은 LES가 사용되었다. MPI의 병렬처리기법을 이용하여 19개의 블록을 각각의 CPU에서 분산처리 하였다. 본 전산수치해석에 사용된 CPU 자원은 Intel 3.0 GHz Dual CPU 10개 (Core 20개)이다.

• 한국전자파학회논문지
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• 제15권10호
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• pp.922-930
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• 2004

본 논문에서는 보다 소형화된 마이크로스트립 패치 안테나를 제작하기 위해 패치 밑면과 접지면 상에 Iris를 수직으로 부착한 3차원 구조의 마이크로스트립 안테나를 설계$\cdot$제작하였다. 부착된 Iris에 의해 패치 밑면에 흐르는 전류의 경로 증가 및 패치 내부의 유전율이 증가되는 효과를 얻고자 하였으며, 제작결과 중심주파수 1.575 GHz에서 높이 9 mm의 평면형 마이크로스트립 패치 안테나(패치 길이 81.5 mm$\times$패치 폭 90 mm)와 비교하여, 지그재그형으로 Iris를 부착한 경우 최대 $79.1\%$(17 mm$\times$90 mm)의 안테나 길이 단축 효과가 나타났다. 이때 측정된 이득 -1.15 dBd, -10 dB 대역폭 $6.2\%$(98 MHz), E-면 HPBW $154^{\circ}$를 나타내어 본 논문에서 제안된 Iris 를 부착한 마이크로스트립 안테나가 소형화에 유효함을 확인하였다.