• Title/Summary/Keyword: 공진파수

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Resonant Characteristics in Rectangular Harbor with Narrow Entrance (1.Field Measurements and Data Analyses) (개구부가 좁은 직사각형 항만의 공진특성(1.현장관측과 자료 분석))

  • 정원무;박우선;서경덕;채장원;정신택
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.11 no.4
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    • pp.201-215
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    • 1999
  • Field measurements were made for long- and short-period waves and current velocities at the harbor mouth using pressure-type wave gauges and a current meter, respectively, at the Gamcheon Harbor which has a rectangular shape with a narrow entrance. The measured pressure data were subjected to spectral analyses after removing tidal effects by applying trend removal and high-pass filtering. For the band averaging of the raw spectra, in order to obtain good resolution over the entire frequency, instead of a constant band width, variable band widths were used, which gradually increase as marching from the lowest frequency towards higher frequencies. The Helmholtz resonance mode at the Gamcheon Harbor shows the relative amplification ratio of 9.2 at the wave period of 31.7 minutes, which is quite large compared with those at the harbors located on the east coast of Korea. The second and the third resonance period was 10.3 and 5.4 minute, respectively. On the other hand, the analysis of every 24 hours data shows that during storms the spectral densities are very large compared to those during calm seas and also the second and third resonances are predominant.

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Temporal characterization of femtosecond laser pulses using spectral phase interferometry for direct electric-field reconstuction (주파수 위상 간섭계를 이용한 펨토초 레이저 펄스의 시간적 특성연구)

  • 강용훈;홍경한;남창희
    • Korean Journal of Optics and Photonics
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    • v.12 no.3
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    • pp.219-224
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    • 2001
  • Spectral phase interferometry for direct electric-field reconstruction (SPIDER) was fabricated and used to characterize pulses from a Ti:sapphire oscillator. In the SPIDER apparatus, two replicas of the input pulse were generated with a time delay of 200 fs and were upconverted by use of sum-frequency generation with a strongly chirped pulse using a 8-cm-long SFIO glass block at a 30-11m-thick type II BBO (p-BaBz04) crystal. The resulting interferogram was recorded with a UV-enhanced CCD array in the spectrometer. The spectral phase was retrieved by SPIDER algorithm in combination with independently measured pulse spectrum and the corresponding temporal intensity profile was reconstructed with a duration of 19 fs. As an independent cross-check of the accuracy of the method, we compared the interferometric autocorrelation (lAC) signal calculated from the SPIDER data with a separately measured lAC. The conventional, but unjustified, method of fitting a sechz pulse to the autocorrelation deceivingly yielded a pulse duration of 15 fs. This systematic underestimation of the pulse duration affirms the need for a complete characterization method. From the consideration in this paper, we concluded that the SPIDER could provide an accurate characterization of femtosecond pulses. ulses.

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Characteristics of High Efficiency Wideband Microstrip Band Pass Filter (고효율 광대역 마이크로스트립 대역통과필터 특성)

  • Lee, Young-Hun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.13 no.4
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    • pp.636-644
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    • 2009
  • This paper presents a compact, low insertion loss, sharp rejection and wide band microstrip band pass filter that is composed rectangular loop resonator and step-impedance-open-stub(SIOS) for wireless data communication. The SIOS can be reduce length about 30% more than general $0.25{\lambda}$ stub. And the stub can the advantage of tuning impedance magnitude. In order to demonstrate agrement of this paper prove, the optimized wide band pass filters are realized and experimented. A transmission line model used to calculate the frequency response of the new filters shows good agreement with measurements. The filter has 3dB fractional bandwith of 52.5%(3.267GHz), an insertion loss of better than 0.33dB from 4.587GHz to 7.854GHz, and two rejection of greater than 30dB within 221MHz$(4.366GHz{\sim}4.587GHz)$ at low frequency band, 181MHz$(7.854GHz{\sim}8.035GHz)$ at high frequency band. Maximum rejection characteristics of the filter are -54dB at low frequency and -60dB at high frequency.

Deformational Characteristics of Cohesive Soils Using Resonant Column / Torsional Shear Testing Equipment (공진주/비틂 전단(RC/TS)시험기를 이용한 점성토의 변형특성)

  • 김동수
    • Geotechnical Engineering
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    • v.11 no.1
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    • pp.113-126
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    • 1995
  • Both resonant column (RC) and torsional shear(TS) tests were performed at small to intermediate strain levels to investigate deformational characteristics of cohesive soils. The effects of variables such as strain amplitude, loading frequency, and number of loading cycles were studied. Plasticity index was found to be an important variables in evaluating these effects. Soils tested include undisturbed silts and clays and compacted subgrade soils. At small strains below the elastic threshold, shear modulus is independent of number of loading cycles and strain amplitude. Small strain material damping exists wi th ranges be tween 1.1% and 1.7% for 75 tests. The elastic threshold strain increases as confining pressure and plasticity index increases. Above the cyclic threshold strain, the modulus of cohesive soil decreases with increasing number of cycles while damping ratio is almost independent of number of load cycles. Moduli and damping ratios of cohesive soils obtanined by RC test are higher than those from 75 test because of the frequency effect. Shear modulus of cohesive soil increases linearly as a function of the logarithm of loading frequency.

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Multi-band Folded Monopole Internal Antenna for Mobile Handset Applications (이동통신 단말기용 다중대역 폴디드 모노폴 내장형 안테나)

  • Kang, Yoon-Ho;Rhyu, Han-Phil;Kong, Ki-Hyun;Park, Myun-Joo;Cheong, Young-Seek;Lee, Byung-Je
    • The Journal of The Korea Institute of Intelligent Transport Systems
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    • v.6 no.2
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    • pp.119-125
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    • 2007
  • In this paper, a multi-band folded planar monopole internal antenna for mobile handset applications is proposed. The proposed antenna has multi-resonances, which is different from a conventional folded monopole antenna, and it provides a wide bandwidth at high frequency bands. The measured impedance bandwidth (VSWR < 3) is 180 MHz and 1880 MHz in lower and higher frequency bands, respectively. The proposed antenna can effectively cover most wireless communication bands including CDMA, GSM, GPS, DCS, PCS, and W-CDMA, WiBro and S-DMB.

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Digital Control of Low-Frequency Square-Wave Two-Stage Electronic Ballast for HID Lamps with Resonant Ignition and High Efficiency (공진 점등 기능과 효율 향상을 위한 HID 램프의 저주파수 구형파 2단 전자식 안정기)

  • Lee, Woo-Cheol
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.27 no.2
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    • pp.69-76
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    • 2013
  • In this paper, electronic ballast using resonant inverter for HID lamp is designed and implemented. The proposed electronic ballast is used the soft switching technology ZVS(Zero Voltage Switching) to reduce turn-on and turn-off loss. The ignition of proposed electronic ballast is achieved by controlling a full bridge inverter which is consisted of LC filter for resonance. After ignition the ballast operates as a low frequency square wave inverter by controlling a full bridge inverter as a buck converter. After ignition at resonant frequency of $f_o$=160kHz, the switching frequency of a buck converter is consisted of 50kHz of high frequency and 170Hz of low frequency. This is for attenuating high frequency harmonics and avoiding acoustic resonance. The experimental results show that electronic ballast using resonant inverter is operated stably.

Dielectric Cover effect of Rectangular Microstrip Patch Antenna on Uniaxial Substrates with Airgap (공기 갭을 갖는 일축성 매질 위에 마이크로스트립 패치 안테나의 덮개층 영향)

  • Yoon, Joong-Han;An, Gyoo-Chul;Kwak, Kyung-Sup
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.38 no.9
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    • pp.29-39
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    • 2001
  • Dielectric cover effect of rectangular microstrip patch antenna on uniaxial substrates with airgap are studied. First, we derive Dyadic Green function for selected anisotropic material by constitutive relation and then formulate integral equations of electric fields using Fourier transform in space region. Using Galerkin's moment method, we discretize the electric field integral equations into the matrix form and select sinusoidal functions as basis functions. We verify the validity of numerical results and compare the results with existing ones in showing a good agreement between them. When the dielectric cover thickness is varied, the resonant frequencies and input impedances in the variation of air gap, patch length and thickness and permittivity of superstrate are presented and analyzed.

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Parammeter Optimization of the Electromagnetically Coupled Broadband Microstrip Antenna by Finite Difference Time Domain Method (시간영역 유한차분법을 이용한 전자기 결합 광대역 마이크로스트립 안테나의 파라메타 최적화)

  • 김정렬;윤현보
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.1
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    • pp.17-27
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    • 1995
  • In this paper, Finite Difference Time Domain (FDTD) method is used to analyze characteristics of the electromagnetically coupled broadband microstrip antenna, and to optimize the antenna parameters. By using short tuning stub in feedline, electromagnetically coupled microstrip antenna shows broadband (approximatcly equal 13%) characteristics, and the characteristics are varied as a function of length, width, and position of the tuning stub. Operating frequency, return loss, VSWR and input impedance are calculated by Fourier transforming the time domain results. Measurement data from fabricated electromagnetically coupled microstrip antenna are compared with FDTD results and are shown to be in good agreement. After optimization of the parameters, maximum bandwidth of about 15% is achieved.

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Design of Transceiver Front-end using Circular Sector Patch Antenna (원형 섹터 패치 안테나를 사용한 트랜시버 전단부 설계)

  • ;Tatsuo Itohv
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.4
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    • pp.807-811
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    • 2001
  • In this paper we proposed a dual-frequency circular sector microstrip antenna with orthogonal polarized modes and high isolation between the two feeding ports. And then we designed a transceiver operating at 5.6 GHz for transmitting and at 5.5 GHz for receiving. The good isolation provided by the proposed antenna is used as the basis for the transmit-receive filtering of transceiver. The operating frequencies and polarization characteristics of the proposed antenna is calculated by using a cavity model. The 5-parameters and radiation patterns of the antenna are measured. A power amplifier and a low noise amplifier are designed and integrated with antenna to make a transceiver, which has about 13dB transmitting gain and about 8㏈ receiving gain.

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Fabrication of GHz-Band FBAR with AIN Film on Mo/SiO2/Si(100) Using MOCVD (Mo/SiO2/Si(100)기판 위에 MOCVD법으로 성장시킨 AIN박막이용 GHz대역의 FBAR제작에 관한 연구)

  • Yang, Chung-Mo;Kim, Seong-Kweon;Cha, Jae-Sang;Park, Ku-Man
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.20 no.4
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    • pp.7-11
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    • 2006
  • In this paper, it is reported that film-bulk-acoustic resonator with high c-axis oriented AIN film on $Mo/SiO_2/Si(100)$ using metal-organic-chemical-vapor deposition was fabricated. The resonant frequency and anti-resonant frequency of the fabricated resonator were observed with 3.189[GHz] and 3.224[GHz], respectively. The quality factor and the effective electromechanical coupling coefficient(${k_{eff}}^2$) were measured with 24.7 and 2.65[%], respectively. The conditions of AIN deposition were substrate temperature of $950[^{\circ}C]$, pressure of 20Torr, and V-III ratio of 25000. A high c-axis oriented AIN film with $4{\times}10^{-5}[\Omega{cm}]$ resistivity of Mo bottom electrode and $4[^{\circ}]$ of AIN(0002) full-width at half-maximum(FWHM) on $Mo/SiO_2/Si(100)$ was grown successfully. The FWHM value of deposited AIN film is useful for the RF band pass filter specification for GHz-band wireless local area network.