• Title, Summary, Keyword: frequency sweep

Search Result 145, Processing Time 0.049 seconds

Study on the Applicability of Reflection Method using Ultrasonic Sweep Source for the Inspection of Tunnel Lining Structure - Physical Modeling Approach - (터널 지보구조 진단을 위한 초음파 스윕 발생원의 반사법 응용 가능성 연구 - 모형실험을 중심으로 -)

  • 김중열;김유성;신용석;현혜자
    • Proceedings of the Korean Geotechical Society Conference
    • /
    • /
    • pp.167-174
    • /
    • 2001
  • Reflection method using ultrasonic source has been attempted to obtain the information about tunnel lining structures composed of lining, shotcrete, water barrier and voids at the back of lining. In this work, two different types of sources, i.e. single-pulse source and sweep source, can be used. Single-pulse source with short time duration has the frequency content whose amplitudes tend to be concentrated around the dominant frequency, whereas sweep source with long time duration denotes a flat distribution of relatively larger amplitude over a broad frequency band, although the peak to peak amplitude of single-pulse source wavelet is equivalent to that of sweep source one. In traditional seismic application, a single-pulse source(weight drop, dynamite) is typically used. However, to investigate the fine structure, as it is the case in the tunnel lining structure, the sweep wavelet can be also a desirable source waveform primarily due to the higher energy over a broad frequency band. For the investigation purposes of sweep source, a physical modeling is a useful tool, especially to study problems of wave propagation in the fine layered media. The main purpose of this work was using a physical modeling technique to explore the applicability of sweep source to the delineation of inner layer boundaries. To this end, a two-dimensional physical model analogous to the lining structure was built and a special ultrasonic sweep source was devised. The measurements were carried out in the sweep frequency range 10 ∼ 60 KHz, as peformed in the regular reflection survey(e.g. roll-along technique). The measured data were further rearranged with a proper software (cross-correlation). The resulting seismograms(raw data) showed quitely similar features to those from a single-pulse source, in which high frequency content of reflection events could be considerably emphasized, as expected. The data were further processed by using a regular data processing system "FOCUS" and the results(stack section) were well associated with the known model structure. In this context, it is worthy to note that in view of measuring condition the sweep source would be applied to benefit the penetration of high frequency energy into the media and to enhance the resolution of reflection events.

  • PDF

Nonlinearity Correction Method in FMCW Laser Range Finder (FMCW 레이저 거리 측정기의 비선형성 보정 방법)

  • Jung, Soo-Yong;Lee, Seong Ro;Jeong, Min A;Park, Chang-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
    • /
    • v.38C no.4
    • /
    • pp.351-358
    • /
    • 2013
  • We propose a correction method of nonlinear frequency sweep in an FMCW(Frequency Modulated Continuous Wave) laser range finder. FMCW laser range finder requires linear frequency sweep for high resolution, and nonlinear frequency sweep makes the system performance degrade. In general, VCO(Voltage Controlled Oscillator) which is a component used for frequency modulation in FMCW method has nonlinear property. To correct the nonlinear frequency sweep, we utilize an auxiliary delay structure for generating trigger signal of ADC(Analog to Digital Converter). Because the trigger signal has same rate of change with the beat signal, the nonlinearity of the beat signal can be corrected. the experimental results show that the proposed method effectively eliminates the nonlinear frequency sweep problem and enhances the system performance.

Millimeter-wave Fast-sweep FM Reflectometry Applied to Plasma Density Profile Measurements

  • Kang, Wook-Kim
    • Journal of electromagnetic engineering and science
    • /
    • v.1 no.1
    • /
    • pp.18-23
    • /
    • 2001
  • A fast-sweep broadband FM reflectometer system has been successfully developed and operacted at the DIII-D tokamak, producing reliable density Profiles with excellent spatial (1 $\leq$ cm) and temporal resolution (~100 $\mu$ s). The system uses a solid-state microwave oscillator and an active quadrupler, covering full Q-band frequencies (33~50 GHz) and providing relatively high output power (20~60 mW). The system hardware allows fu11band frequency sweep in 10 $\mu$ s, but due to digitization rate limit on DIII-D, sweep time was limited to 75~100 $\mu$ s. Fast frequency sweep has helped to reduce density fluctuation effects on the reflectometer phase measurements, thus improving reliability for individual sweeps. The fast-sweep system with high spatial and temporal resolution has allowed to measure fast-changing edge density profiles during plasma ELMS and L-H transitions, thus enabling fast-time sca1e physics studies.

  • PDF

Sine sweep effect on specimen modal parameters characterization

  • Roy, Nicolas;Violin, Maxime;Cavro, Etienne
    • Advances in aircraft and spacecraft science
    • /
    • v.5 no.2
    • /
    • pp.187-204
    • /
    • 2018
  • The sine sweep base excitation test campaign is a major milestone in the process of mechanical qualification of space structures. The objectives of these vibration tests are to qualify the specimen with respect to the dynamic environment induced by the launcher and to demonstrate that the spacecraft FE model is sufficiently well correlated with the test specimen. Dynamic qualification constraints lead to performing base excitation sine tests using a sine sweep over a prescribed frequency range such that at each frequency the response levels at all accelerometers, load cells and strain gages is the same as the steady state response. However, in practice steady state conditions are not always satisfied. If the sweep rate is too high the response levels will be affected by the presence of transients which in turn will have a direct effect on the estimation of modal parameters. A study funded by ESA and AIRBUS D&S was recently carried out in order to investigate the influence of sine sweep rates in actual test conditions. This paper presents the results of this study along with recommendations concerning the choice of methods.

A Study on X-band Frequency Synthesizer for Radar Transceiver (레이더 송수신기용 X 밴드 주파수 합성기에 관한 연구)

  • Park, Dong-Kook;Lee, Hyun-Soo
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.30 no.3
    • /
    • pp.444-448
    • /
    • 2006
  • In this paper, a frequency synthesizer for X-band FMCW radars is proposed. Some X-band FMCW radars have been used as a level sensor for tanker ship and the resolution of the level sensor may be mainly depend on linearity of frequency sweep. For a linear frequency sweep. the proposed synthesizer employs a phase-locked loop using prescalars and a high speed digital PLL chip. The measured results show that the linear frequency sweep range is from 10 GHz to 11 GHz and the output power of the synthesizer is minium 7 dBm. and the phase noise is about -80 dBc/Hz at 100 KHz offset from 11 GHz.

A Novel High Speed Frequency Sweeping Signal Generator in X-band Based on Tunable Optoelectronic Oscillator

  • Sun, Mingming;Chen, Han;Sun, Xiaohan
    • Current Optics and Photonics
    • /
    • v.2 no.1
    • /
    • pp.53-58
    • /
    • 2018
  • A novel X-band high speed frequency sweep signal generator based on a tunable optoelectronic oscillator (OEO) incorporating a frequency-swept laser is presented and the theoretical fundamentals of the design are explained. A prototype of the generator with tuning range from 8.8552 GHz to 10.3992 GHz and a fine step about 8 MHz is achieved. The generated radiofrequency signal with a single sideband (SSB) phase noise lower than -100 dBc/Hz@10KHz is experimentally demonstrated within the whole tunable range, without any narrow RF band-pass filters in the loop. And the tuning speed of the frequency sweep signal generator can reach to over 1 GHz/s benefiting from applying a novel dispersion compensation modular instead of several tens of kilometers of optical fiber delay line in the system.

Viscoelastic properties of electrorheological fluids (전기유변유체의 점탄성 특성에 관한연구)

  • Choe, Yun-Dae;Kim, Sang-Guk
    • Korean Journal of Materials Research
    • /
    • v.2 no.3
    • /
    • pp.220-227
    • /
    • 1992
  • Electrorheological(ER) fluid's storage shear modulus(G') and loss factor(${\eta}$) have been directly measured using small amplitude forced oscillating rheometer as a function of oscillating frequency, strain amplitude and applied electric field. Two types of experiment were performed , (a) frequency sweep and (b) amplitude sweep. Two kinds of sample were employed for this experiment ; cornstarch particles in corn oil and zeolite particles in silicone oil. The storage shear modulus was a strong function of driving frequency. Generally, the modulus increased with driving frequency. On the other hand, the loss factor was not well behaved as storage modulus, but as the driving frequency increases the loss factor slightly decreases was the trend of the material's characteristics. Also the modulus was a strong function of strain amplitude. Generally, modulus decreased with increasing strain, but loss factor increases slightly with increasing strain amplitude. For G', cornstarch in corn oil ER fluid has higher values than zeolite based fluid as we increased applied electric field. On the other hand, zeolite based fluid has higher values for ${\eta}$. There is a reasonable agreement between theoretical calculation and experiment.

  • PDF

A high Efficient Solver for High-Frequency Response Analysis of MEMS Resonators (MEMS 공진기의 고주파 응답해석을 위한 고효율 해석기)

  • Ko, Jin-Hwan;Bai, Zhaojun
    • Proceedings of the KSME Conference
    • /
    • /
    • pp.467-472
    • /
    • 2007
  • A modern MEMS resonator is a micro-scale structure operated over a high frequency range. In order to predict its resonant behavior in a design process, High-frequency response analysis (Hi-FRA) is demanded. Algebraic substructuring (AS) is known as a fast numerical technique to construct an eigenspace for FR and frequency sweep (FS) algorithm efficiently solves the frequency response system projected on the eigenspace. However, the existing FS algorithm using AS is developed for low-FRA, say over the range 1Hz-2KHz. In this work, we extend the FS algorithm using AS for FRA over an arbitrary frequency range. Therefore, it can be efficiently applied to systems operated at a high frequency, say over the range 230MHz-250MHz. The success of the proposed method is demonstrated by Hi-FRA of a checkerboard resonator.

  • PDF

Prediction of Change in Equivalent Circuit Parameters of Transformer Winding Due to Axial Deformation using Sweep Frequency Response Analysis

  • Sathya, M. Arul;Usa, S.
    • Journal of Electrical Engineering and Technology
    • /
    • v.10 no.3
    • /
    • pp.983-989
    • /
    • 2015
  • Power transformer is one of the major and key apparatus in electric power system. Monitoring and diagnosis of transformer fault is necessary for improving the life period of transformer. The failures caused by short circuits are one of the causes of transformer outages. The short circuit currents induce excessive forces in the transformer windings which result in winding deformation affecting the mechanical and electrical characteristics of the winding. In the present work, a transformer producing only the radial flux under short circuit is considered. The corresponding axial displacement profile of the windings is computed using Finite Element Method based transient structural analysis and thus obtained displacements are compared with the experimental result. The change in inter disc capacitance and mutual inductance of the deformed windings due to different short circuit currents are computed using Finite Element Method based field analyses and the corresponding Sweep Frequency Responses are computed using the modified electrical equivalent circuit. From the change in the first resonant frequency, the winding movement can be quantified which will be useful for estimating the mechanical withstand capability of the winding for different short circuit currents in the design stage itself.

System Performance Analysis for Multi-Band SweepSAR Operating Mode (다중대역 SweepSAR 운용 모드의 시스템 성능 분석)

  • Yoon, Seong-Sik;Lee, Jae-Wook;Lee, Taek-kyung;Ryu, Sang-Burm;Lee, Hyeon-Cheol;Kang, Eun-Su;Lee, Sang-Gyu
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.28 no.3
    • /
    • pp.186-194
    • /
    • 2017
  • In this paper, we analyze the main performance of satellite's Synthetic Aperture Radar system for high resolution and wide swath. We have used the radiation pattern of reflector antenna with array feed and comparison between the conventional ScanSAR mode and SweepSAR mode has been carried out. The SweepSAR mode is a high-resolution wide-swath mode that transmits beams over a wide range and receives echo signals through sequential beamforming based on SCORE(SCan On REceive). In this paper, we analyzed the operating principle and characteristics of satellite's SweepSAR mode and simulate system performances. In addition, in order to increase the utilization of image, performances analysis for multiple frequency bands(C-band, X-band) has been considered.