• 제목/요약/키워드: Coupling loss

Search Result 589, Processing Time 0.031 seconds

Dielectric Thin Film Mirror Embedded Optical Fiber Couplers (유전체 박막 거울 내장형 광섬유 결합기)

  • 신종덕
    • Korean Journal of Optics and Photonics
    • /
    • v.4 no.4
    • /
    • pp.420-427
    • /
    • 1993
  • Dielectric thin film mirrors are embedded in multimode and single-mode fibers by a fusion splicing technique. The fibers with $45{\circ}$ angled embedded mirrors serve as ultra-compact directional couplers with low excess optical loss of 0.2 dB for multimode and 0.5 dB for single mode at 1.3 ${\mu}m$ and excellent mechanical properties. The reflectance is wavelength dependent and strongly polarization depencient. Far-field scans of the reflected output power measured with a white-light source show a pattern which is almost circularly symmetric with aspect ratio of 1.09 at 5% of the peak power. The splitting ratio in a multimode coupler measured with a diode laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers, indicating that these couplers are less susceptible to modal noise occuring in optical fiber communication systems. Spectral properties of multilayer internal mirrors normal to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results.

  • PDF

Design of the Electromagnetic Coupling Wideband Microstrip Antenna using FDTD Method (FDTD 법을 이용한 광대역 전자기 결합 마이크로스트립 안테나의 설계)

  • Jang, Yong-Woong;Shin, Ho-Sub;Kim, Nam;Park, Ik-Mo;Shin, Chull-Chai
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.9 no.4
    • /
    • pp.473-482
    • /
    • 1998
  • In this paper, characteristics of the wide band microstrip antennas with parasistic element are analyzed by the Finite Difference Time Domain(FDTD) method, and antenna parameters are optimized to get maximum bandwidth, retern loss, input impedance, and radiation pattern are calculated by Founier transforming the time domain results. The characteristics of the antenna are varied and the bandwidth of the antenna is broaded as a length and a width of the driven element, a gap of the driven element and the parasitic element, a width and a length of parasitic element. So the different patchs are resonating at different frequencies and this multipule resonance increase the bandwidth. The Results of the calculation and measurement, the size of the antenna with parasitic element is about a twice larger than a microstrip antenna, but bandwidth is four times better than a microstrip antenna. And these results were in relatively good accordance with the measured values.

  • PDF

Design of the Near Field Microwave Guide Type of Probe Having Enhanced High Transmission Efficiency and Smaller Beam Spot Area (고 투과 효율과 소형 빔 스팟 면적을 갖는 근접장 마이크로웨이브 도파관 탐침의 설계)

  • Ko, Ji-Hwan;Cho, Young-Ki
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.26 no.12
    • /
    • pp.1058-1063
    • /
    • 2015
  • In this article, we propose a near field microwave scanning probe structure in which two short conducting rods are attached to the center of the ridged(H-type) aperture, thereby reducing significantly the beam spot area while maintaining the high transmission efficiency through the output coupling H-type(ridged) aperture. Here the two short parallel conducting rods seem to play an important role of concentrating the transmitted electromagnetic energy through the H-type aperture and so reducing the beam area for high resolution. For validation of the proposed theory, the near field waveguide probe is fabricated according to the simulated results and its return loss characteristics versus frequencies are measured. The comparison between theory and experiment is seen to be in good agreements.

A Study on the High Frequency Resonant Inverter of Class D SEPP type using LS-ZVS-LSTC (LS-ZVS-LSTC를 이용한 D급 SEPP형 고주파 공진 인버터에 관한 연구)

  • Park, Dong-Han;Choi, Byeong-Joo;Kim, Jong-Hae
    • Journal of IKEEE
    • /
    • v.24 no.1
    • /
    • pp.260-268
    • /
    • 2020
  • This paper presents the high frequency resonant inverter of class D SEPP(Single-Ended Push Pull) type using LS-ZVS-LSTC, which can reduce the switching losses during the turn-on and turn-off switching time. The analysis of high frequency resonant inverter using LS-ZVS-LSTC(Low-loss Turn-off Snubber Capacitor) proposed in this paper is described in general by adopting the normalized parameters. The operating characteristics of the proposed high frequency resonant inverter were also evaluated by using the control parameters such as the normalized control frequency(μ), the normalized load time constant(τ), the coupling factor(κ) and so on. Based on the characteristic values through the characteristics of evaluation, an example of the design method of the 1.8[kW] class D SEPP type high frequency inverter is suggested, and the validity of the theoretical analysis is verified using the experimental data.

An Agent-Based Modeling Approach for Estimating Inundation Areas over Time (행위자 기반 모델링을 활용한 시간에 따른 침수 지역 예상)

  • Kim, Byungil;Shin, Sha Chul;Jung, Jaehoon
    • Korean Journal of Construction Engineering and Management
    • /
    • v.17 no.4
    • /
    • pp.20-27
    • /
    • 2016
  • Emergency and evacuation planning is critical to reduce potential loss of life from flooding. In order to develop evacuation plans, emergency managers and decision makers require estimates of probable inundation areas and times of inundation. In this paper, we present an agent-based modeling approach that incorporates in a hydrodynamic model to estimate both of these properties. A case study is conducted modeling the failure of a dam located in Andong, South Korea. We estimate flood travel times for Manning's roughness coefficients and discharge using a coupling of the continuity equation and Manning's equation. Using the output from the hydrodynamic model and the flood travel times, the agent-based model produces flood inundation maps at each time interval. The model estimates that for two-thirds of the Andong region the time of inundation is estimated to be slightly less than three minutes. The results of this study can be used to in the development of emergency and evacuation planning for the region.

Linear Stability Analysis for Combustion Instability in Solid Propellant Rocket (고체추진 로켓의 선형 안정성 요소에 대한 연구)

  • Kim, Hakchul;Kim, Junseong;Moon, Heejang;Sung, Honggye;Lee, Hunki;Ohm, Wonsuk;Lee, Dohyung
    • Journal of the Korean Society of Propulsion Engineers
    • /
    • v.17 no.5
    • /
    • pp.27-36
    • /
    • 2013
  • Linear stability analysis for combustion instability within a cylindrical port of solid rocket motor has been conducted. The analysis of acoustic energy has been performed by a commercial COMSOL code to obtain the mode function associated to each acoustic mode prior to the calculation of stability alpha. An instability diagnosis based on the linear stability analysis of Culick is performed where special interests have been focused on 5 stability factors(alpha) such as pressure coupling, nozzle damping, particle damping and additionally, flow turning effect and viscous damping to take into account the flow and viscosity effect near the fuel surface. The instability decay characteristics depending on the particle size is also analyzed.

Current effects on global motions of a floating platform in waves

  • Shen, Meng;Liu, Yuming
    • Ocean Systems Engineering
    • /
    • v.7 no.2
    • /
    • pp.121-141
    • /
    • 2017
  • The purpose of this paper is to understand and model the slow current (~2 m/s) effects on the global response of a floating offshore platform in waves. A time-domain numerical simulation of full wave-current-body interaction by a quadratic boundary element method (QBEM) is applied to compute the hydrodynamic loads and motions of a floating body under the combined influence of waves and current. The study is performed in the context of linearized potential flow theory that is sufficient in understanding the leading-order current effect on the body motion. The numerical simulations are validated by quantitative comparisons of the hydrodynamic coefficients with the WAMIT prediction for a truncated vertical circular cylinder in the absence of current. It is found from the simulation results that the presence of current leads to a loss of symmetry in flow dynamics for a tension-leg platform (TLP) with symmetric geometry, resulting in the coupling of the heave motion with the surge and pitch motions. Moreover, the presence of current largely affects the wave excitation force and moment as well as the motion of the platform while it has a negligible influence on the added mass and damping coefficients. It is also found that the current effect is strongly correlated with the wavelength but not frequency of the wave field. The global motion of a floating body in the presence of a slow current at relatively small encounter wave frequencies can be satisfactorily approximated by the response of the body in the absence of current at the intrinsic frequency corresponding to the same wavelength as in the presence of current. This finding has a significant implication in the model test of global motions of offshore structures in ocean waves and currents.

Active optical coupler using the side polished single mode fiber and thermo-optic polymer multimode planar waveguide (측면 연마된 단일모드 광섬유와 열 광학 다중모드 평면도파로를 이용한 능동형 광 결합기)

  • 김광택;유호종;김성국;이소영;송재원;이상재;김시홍;강신원
    • Korean Journal of Optics and Photonics
    • /
    • v.10 no.3
    • /
    • pp.248-253
    • /
    • 1999
  • In this paper, we have investigated a fiber type active coupler which utilizes the mode coupling between the side polished single mode optical fiber and the active multimode planar waveguide. The proposed device can be used for not only tunable wavelength filter or optical intensity modulator but also a tool for measuring optical properties of guiding material such as refractive index, birefringence, electro-optic coefficient, and thermo-optic coefficient. We gave designed and optimized a coupler structure using the BPM and fabricated the device using thermo-optic polymer as active planar waveguide overlay. The device showed that insertion loss was less then 0.5 dB, extinction ratio was -13 dB at the resonance wavelength, and the wavelength tunablity due to thermo-optic effect was -1.5 nm/$^{\circ}C$. The active coupler using thermo-optic effect can be used as a wavelength tunable filer, an optical intensity modulator and an optical sensor. pulses that are subsequently compressed by a dispersive optical fiber. Experimental results show that $sech^2$ shape pulses with a pulse width of ~14 ps and a time bandwidth product of ~0.34 are successfully generated at 10 GHz repetition rate. In contrast to other methods, such as higher order soliton compression, this approach does not depend on the optical power and thus shows promise for application to low-power lasers.

  • PDF

Frequency Sharing of Cellular TDD-OFDMA Systems beyond 3G with Terrestrial Fixed Systems (TDD-OFDMA 기반의 차세대 셀룰라 시스템과 육상 고정 시스템 간의 주파수 공유 분석)

  • Jo, Han-Shin;Yoon, Hyun-Goo;Yook, Jong-Gwan
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.32 no.1A
    • /
    • pp.125-133
    • /
    • 2007
  • In this paper, the frequency sharing issue between cellular time division duplex-orthogonal frequency division multiple access (TDD-OFDMA) Systems and terrestrial Fixed Systems has been studied. The conventional advanced minimum coupling loss (A-MCL) includes only the formulation to calculate the interference from one interfering system. Therefore, A-MCL must be modified to assess the aggregated interference from base stations(BS) and mobile stations(MS). By applying the modified model, the coexistence analysis are done according to the average number of MS per sector, BS-to-BS distance, and the main beam direction of the terrestrial fixed system. In the case of 20 MS per sector, the BS-to-BS distance and the minimum distance between a terrestrial fixed system and BS are 5.8 km and 2.5 km, respectively. It is about 25dB that the difference between maximum and minimum interference signal power which varies with the main beam direction of the terrestrial fixed system. Moreover, for 40% of the main beam direction of the terrestrial fixed system, interference signal power is less than the maximum permissible interference.

Preparation and Characterization of Swallow-Tail Terrylene Bisimide as Organic Phosphor (Swallow-Tail Terrylene Bisimide 적색 유기 형광체 제조 및 특성 연구)

  • Jung, Sung Bong;Jeong, Yeon Tae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.33 no.3
    • /
    • pp.194-200
    • /
    • 2020
  • Perylene bisimide derivatives are developed for red organic phosphor because of their advantages, such as excellent luminous efficiency and high thermal stability. Despite these advantages, they have poor solubility characteristics in organic solvents and short emission wavelength as red organic phosphor for hybrid light-emitting diodes (LEDs). In this study, we prepared terrylene bisimide using a coupling reaction and swallow-tail imide group, which has excellent solubility. The structures and properties of swallow-tail terrylene bisimide (9C) were analyzed using 1H-nuclear magnetic resonance (1H-NMR), Fourier-transform infrared (FT-IR), UV/Vis spectroscopy, and thermal gravimetric analysis (TGA). The maximum absorption wavelength of (9C) in the UV/Vis spectrum was 647 nm, and the maximum emission wavelength was 676 nm. In the TGA, (9C) demonstrated good thermal stability with less than 5 wt% weight loss up to 415℃. In the solubility test, (9C) has a good solubility of more than 5 wt% in chloroform and dichloromethane. When the compounds (9C) were mixed with PMMA (polymethly methacrylate), the films showed peaks at 680 nm in the PL spectra. The results verify the suitability of (9C) as a red organic phosphor for hybrid LEDs.