• Journal of the Korean earth science society
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• v.43 no.2
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• pp.239-252
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• 2022

Quality control methods for the first G-band vapor radiometer (GVR) mounted on a weather aircraft in Korea were developed using the GVR Precipitable Water Vapor (PWV). The aircraft attitude information (degree of pitch and roll) was applied to quality control to select the shortest vertical path of the GVR beam. In addition, quality control was applied to remove a GVR PWV ≥20 mm. It was found that the difference between the warm load average power and sky load average power converged to near 0 when the GVR PWV increased to 20 mm or higher. This could be due to the high brightness temperature of the substratus and mesoclouds, which was confirmed by the Communication, Ocean and Meteorological Satellite (COMS) data (cloud type, cloud top height, and cloud amount), cloud combination probe (CCP), and precipitation imaging probe (PIP). The GVR PWV before and after the application of quality control on a cloudy day was quantitatively compared with that of a local data assimilation and prediction system (LDAPS). The Root Mean Square Difference (RMSD) decreased from 2.9 to 1.8 mm and the RMSD with Korea Local Analysis and Precipitation System (KLAPS) decreased from 5.4 to 4.3 mm, showing improved accuracy. In addition, the quality control effectiveness of GVR PWV suggested in this study was verified through comparison with the COMS PWV by using the GVR PWV applied with quality control and the dropsonde PWV.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.58-62
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• 1999

We fabricated a new hairpin type HTS 2-pole microstrip Bandpass filter to operate at 5.8GHz. The fabrication method was pulsed laser deposition and YBCO films were deposited on ${\alpha}$-A1$_2O_3$ substrates with a CeO$_2$ thin layer as a buffer layer. We developed a new style hairpin type filter by using interdigitide innerpole. Compared to the saute size regular hairpin type filters, our filter had a lower center frequency, bandwidth and loss by an amount of 14.5%, 29.6%, 0.5488dB, respectively. The size of the filters were 13.7${\times}$3.3mm. We did simulations on the several types of band pass filters by using HFSS and serenade. We measured growth rate and Tc of YBCO films grown on CeO$_2$/ ${\alpha}$-A1$_2O_3$ substrates which were rotated while growing films.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.119-123
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• 2005

In this paper. It is proposed and fabricated that the new antenna of dual T type structure is shifted easily center frequency. This antenna consists of dual dipoles resemblance to dual T type, which are fed by a coplanar waveguide (CPW) on signal plane. The analyzed and measured characteristic of new antenna is controled between distance of two dipoles for shifting center frequency. The proposed antenna is 450MHz bandwidth for using IMT2000 band. The characteristic parameters of the proposed antenna are analyzed by using a FDTD methods.

• Journal of the Optical Society of Korea
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• v.20 no.1
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• pp.135-139
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• 2016

I propose a vector passive harmonic mode-locked fiber laser based on topological insulator Bi2Se3 interacting with a fiber taper with a diameter of 7 μm. The particles of topological insulator are deposited uniformly onto the fiber taper with light pressure effect. By incorporating the fabricated saturable absorber into an Er-doped fiber laser cavity, stable mode-locked fiber is obtained. Due to the intense evanescent field of the fiber taper, strong confinement of light enhances the nonlinearity of the laser cavity, and passive harmonic mode-locking is performed. I observe a maximum harmonic mode-locking of 356th, corresponding to a frequency of 3.57 GHz. The pulse duration is 824 fs, and the full width at half maximum of the spectrum is about 8.2 nm. The polarization dependent loss of the saturable absorber is ~ 2.5 dB in the wavelength range of the C band. As the cavity contains no other polarization dependent device, the mode-locked laser is functioning in the vector state. The harmonic order vs pump power is investigated. To the best of our knowledge, this report is the highest frequency mode-locked fiber laser based on Bi2Se3. Experimental results indicate that the topological insulator Bi2Se3 functioning with a thin fiber taper is effective for vector harmonic mode-locking.

• Nuclear Engineering and Technology
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• v.38 no.8
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• pp.785-792
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• 2006

The microwave heating system of KSTAR consists of ECH and LHCD. ECH and LHCD offer the benefits ofa reliable operation at the start of plasma formation and a non-inductive current drive durable steady state operation, respectively. LHCD uses a C-band microwave system with a frequency of 5 GHz. A pulsed power modulator with a power of 3.6 MW, $4{\mu}S$, 200 pps is required to drive the high-powered magnetron. The development of a pulse modulator with 1:4 pulse transformers is the focus of the research in this study. The peak power handling capability is 3.6 MW (45 kV, 90 A at load side with a pulse width of $4{\mu}S$). This paper describes the system overview and test results of the pulsed modulator. In particular, a simulated waveform is compared with the tested waveform.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.93-93
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• 2000

수소화된 비정질 탄소(a-C:H)는 그 증착 조건에 따라서 여러 가지 다른 구조와 특성을 갖게 되며, 특히 DLC(diamond-like carbon) 및 CNT(Carbon nanotube)는 FED (field emission display) 개발 면에서 중요하게 연구되고 있다. 우리는 a-C:H 박막을 PECVD (plasma-enhanced chemical vapor deposition) 방법으로 증착하고 CH4 가스를 사용하였고 기판 온도는 상온-32$0^{\circ}C$ 사이에서 변화되었다. 기판은 Corning 1737 glass, quartz, Si, Ni 등을 사용하였다. 증착 압력과 R.F. power는 각각 0.1-1 Torr 와 12-60w 사이에서 변화되었다. ESR 측정은 X-band(주파수 약 9 GHz)에서 그리고 상온에서 행해졌다. 상온에서의 스핀밀도는 약한-표준피치(weak-pitch standard) 스펙트럼과 비교하여 얻을 수 있었다. 그리고 a-C:H 박막의 구조는 He-Ne laser(파장 632.8 nm)를 이용하는 micro-Raman spectroscopy로 분석하였다. 증착조건에 따른 스핀밀도의 변화 및 Raman 스펙트럼에서의 D-peak, G-peak의 위치 및 반치록, I(D)/I(G) 등을 조사하였다. 증착된 a-C:H 박막은 R.F.power가 증가할수록 대체로 스핀밀도가 증가하였으며, Raman 스펙트럼에서의 I(D)/I(G) 비율은 대체로 감소하였다. 증착된 박막들은 polymer-like Carbon으로 추정되었으며, 스핀밀도가 증가할수록 대체적으로 흑연 구조 영역이 증가됨을 알 수 있었다. 또한 glass나 Si 기판에 비해 Ni 기판위에서 polymer-like Carbon 구조는 향상되는 경향을 보였다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.8
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• pp.36-44
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• 1999

This paper presents the design and fabrication of the duplexer for a Ka-band satellite transponder which is analyzed transmission characteristics by calculating the generalized scattering matrix using mode matching method. It is composed of 2 bandpass filters, coupled with H-plane T-junction having symmetrical inductive iris and E-plane metal insert structures. Compared with the size and weight of the Rx and Tx filter loaded with a transponders respectively, those of the duplexer can be effectively reduced. In a high power transmission, the variation of the filter characteristics is minimized by the scheme that irises are extended to the exterior of H-plane of the waveguide. This scheme needs no extra heat sinks for dissipating high power. The duplexer is designed to improve the simplification, durability and reliability by eliminating tuning screws, which have been used to compensate for the characteristics of fabricated filters. The bandpass filters of the duplexer show the insertion loss of less than 1.2 dB and the return loss in excess of 15 dB. The isolations of more than 65 dB have been achieved between Rx and Tx filter.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.63-70
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• 2005

We investigated the phase noise of an oscillator with a extremely high-Q resonator used as the resonant element. A TE$_{011}$ mode rutile-loaded resonator with high-temperature superconductive (HTS) $YBa_2Cu_3O_{7-\delta}$(YBCO) films used as the endplates is prepared for this purpose. At 23.5 K, the unloaded Q and the loaded Q are 863000 and 180000, respectively. The phase noise of -104.8 dBc/Hz at 1 KHz offset was observed for the oscillator having a resonator with $Q_{L}$ =180000 at the $TE_{01\delta$ mode resonant frequency of 8.545 GHz at 23.5 K Such oscillators with very low phase noise are expected to be used for building up communication systems capable of efficient use of the frequency band and high-speed data transmission as well as for Doppler radars. Frequency tuning could be realized for the resonator by using a piezoactuator Applicability of the tunable rutile resonator for fabricating tunable oscillators of high performances is discussed.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.153-156
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• 2008

본 논문은 Local oscillator의 2차 harmonic 신호를 이용하고 Dual gate FET 형태를 이용한 이중대역 주파수 혼합기 설계에 대한 연구 이다. 기존의 회로 구조는 두 대역을 처리하기 위해 각각 두 개의 국부 발진기와 혼합기를 사용함으로 인하여 구조의 복잡함과 큰 전력 손실이라는 단점을 가지고 있었다. 본 연구는 하나의 주파수 혼합기로 두 개의 대역에서 동시에 적용할 수 있는 Concurrent 이중 대역 설계 연구를 하였다. ISM(Industrial Science Medical) 대역 인 912MHz, 2.45GHz의 RF 입력과 455.5MHz, 1224.5MHz의 LO 입력 신호에서 동일한 IF인 1MHz로 하향변환 했을 때 모의실험 결과 변환이득은 각각 7dB, 12dB로 이고 RF-LO 격리도는 -29dB, -24.7dB가 나왔다. 또한 두 입력 단에서의 반사손실의 -15dB 이상을 얻었다. 또한 각각의 대역에서 잡음지수는 8.5dB, 6.26dB이다.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.58-63
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• 2013

Since radio interference can degrade the performance of systems or limit the system operation, an accurate assessment of radio interference with the existing systems should be conducted prior to the operation of a new system. In this paper, we present an evaluation methodology for the radio interference between radio-navigation satellite service (RNSS) systems and mobile communication service (MS) system. Radio interferences from RNSS systems into MS system using minimum coupling loss (MCL) method are simulated and vice-versa, and the frequency sharing condition between two systems are derived in a same geographical area.