• Title/Summary/Keyword: low frequency

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A Study on Low Phase Noise Frequency Synthesizer Design for Satellite Terminal (위성통신 단말용 저 위상잡음 주파수 합성기 설계에 관한 연구)

  • Ryu, Joon-Gyu;Oh, Deock-Gil;Hong, Sung-Yong
    • Journal of Satellite, Information and Communications
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    • v.6 no.1
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    • pp.45-49
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    • 2011
  • In this paper, we present the high resolution and low phase noise frequency synthesizer for satellite terminal. To improve the phase noise of frequency synthesizer, we analyze how the configuration of frequency synthesizer affect the phase noise. The implemented frequency synthesizer reduce the phase noise and show the high resolution. The output power of this frequency synthesizer is over -2dBm in 950~1450MHz and the phase noise of the -101dBc/Hz at 10kHz frequency offset.

STF-OFDM Transmission Scheme via Preceding in Frequency Domain (주파수 영역에서의 사전 부호화를 이용한 STF-OFDM 전송 기법)

  • 박상순;김한경;백흥기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.7C
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    • pp.954-961
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    • 2004
  • In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. The STF-OFDM transmission scheme that we propose in this paper is a simple transmission cheme for achieving frequency diversity gain with low complexity. Using preceding in frequency domain, we obtain frequency diversity gain and improve the SER performance of conventional ST-OFDM. The preceding scheme proposed in this paper is a very simple method that can be encoded and decoded with low complexity.

Design and Implementation of a Novel Frequency Modulation Circuit using Phase Locked Synthesizer (PLL Synthesizer를 이용한 새로운 FM 회로 설계 및 제작)

  • Yang, Seong-Sik;Lee, Jong-Hwan;Yeom, Kyung-Whan
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.224-228
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    • 2003
  • In this paper, for phase lock loop(PLL) synthesizer, we introduce a novel but simple and low cost frequency modulation(FM) circuit of a flat peak frequency deviation for modulation signal from high to very low frequency penetrating into the loop-bandwidth of PLL. The FM circuit was basically designed to compensate an amount of feedback of the loop filter in PLL. The circuit also includes the capability of the adjustment of peak frequency deviation and blocking the interference with the loop filter. The designed circuit was successfully implemented and showed the flat frequency deviation as expected in the design.

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An Improvement Parallel to the Efficiency of Boost Converter for Power Factor Correction (PFC용 부스트 컨버터의 병렬화에 의한 효율 개선)

  • 전내석;장수형;전일영;박영산;안병원;이성근;김윤식
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.11a
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    • pp.120-124
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    • 2001
  • A new technique for improving the efficiency of single-phase high-frequency boost converter is proposed. This converter includes an additional low-frequency boost converter which is connected to the main high-frequency switching device in parallel. The additional converter is controlled at lower frequency. Most of the current flows in the low-frequency switch and so, high-frequency switching loss is greatly reduced accordingly Both switching device are controlled by a simple method; each controller consists of a one-shot multivibrator, a comparator and an AND gate. The converter works cooperatively in high efficiency and acts as if it were a conventional high-frequency boost converter with one switching device. The proposed method is verified by simulation. This paper describes the converter configuration and design, and discusses the steady-state performance concerning the switching loss reduction and efficiency improvement.

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Frequency Analysis of EMG Signals using Power Spectral Density (전력 스펙트럼 밀도를 이용한 근전도 신호의 주파수 해석)

  • 박상희;변윤식
    • Journal of Biomedical Engineering Research
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    • v.6 no.1
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    • pp.19-30
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    • 1985
  • This paper describes the EMG signals in frequency domain using power spectral density, The changes in the moan frequency can represent the energy distribution which results from changing in load before and during fatigue. Most of EMG signal power spectrum is located between 10 and 200Hz. Shifts of the high-energy regions of the power spectra can be inferred from the changes in the mean frequency. If the load is increased without fatigue-ocurring, the high frequency regions have more energy than the low frequency regions. And if load is increased during fatigue, the low frequency regions have more energy than the high frequency regions.

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Frequency-dependent electrical parameters of soils as a function of the moisture content (수분함유량에 따른 토양의 전기적 파라미터의 주파수의존성)

  • Lee, Bok-Hee;Kim, Ki-Bok
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.28 no.6
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    • pp.68-74
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    • 2014
  • The electrical parameters of soils are highly dependent on the various factors such as types of soil, chemical compositions, moisture content, temperature, frequency, and so on. The analysis of soil parameters is of fundamental importance in design of grounding systems. In this paper, we present the experimental results of frequency-dependent impedance, resistivity, permittivity of soils as functions of types of soil and moisture content. The impedance and resistivity of soils are decreased as the moisture content and the frequency increase. In particular, the variation of the soil resistivity with the frequency is pronounced in the conditions of high resistivity and low moisture content. On the contrary, the permittivity of soils are sharply decreased with increasing the frequency below 10kHz and the frequency-dependent permittivity of soils are highly changed in the conditions of high moisture and low resistivity.

A Study on Transition From Cycle-dependent to Time-dependent Crack Growth in SUS304 Stainless Steel (SUS304강의 사이클의존형에서 시간의존형균열성장으로의 천이에 관한 연구)

  • 주원식;조석수
    • Journal of Welding and Joining
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    • v.14 no.1
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    • pp.38-46
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    • 1996
  • High temperature low cycle fatigue crack growth behavior is investigated over a range of two temperatures and various frequencies in SUS 304 stainless steel. It is found that low frequency and temperature can enhance time-dependent crack growth. With high temperature, low frequency and long crack length, ${\Delta}J_c/{\Delta}J_ f$, the ratio of creep J integral range to fatigue J integral range is increased and time-dependent crack growth is accelerated. Interaction between ${\Delta}J_f$ and ${\Delta}J_c$ is occured at high frequency and low temparature and ${\Delta}J_c$, creep J integral range is fracture mechanical parameter on transition from cycle-dependent to time dependent crack growth in creep temperature region.

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Implementation of Platform for Low Rate WPAN System (저속 WPAN 시스템 구현을 위한 플랫폼 설계)

  • Park, Joo-Ho;Kim, Myoung-Jong;Kim, Jae-Young
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.133-134
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    • 2006
  • In this paper the platform system for IEEE 802.15.4 Low Rate WPAN is designed and fabricated. IEEE 802.15.4 Low Rate WPAN system serves the functions and realization of home-area network. According to the IEEE 802.15.4 standard, there are two modes, One is BPSK modulation in 868/915MHz frequency band. The other is O-QPSK modulation in 2.45GHz frequency band. In this paper we implemented the platform system mounted in one PCB board in 868/915MHz frequency band of IEEE 802.15.4 Low Rate WPAN system. We measured that the platform system which consists of digital part and RF part has good performance. Also RF part is realized by design and fabrication of the RF transceiver IC. The key issue is to make the platform system which provides the function of Low Rate WPAN system to meet the requirement of IEEE 802.15.4 standards.

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Adaptation of Sensory Nerve Afferents for Selective Elicitation of Tactile Sensations (감각의 순응을 이용한 선택적 감각유발 가능성)

  • An, Boyoung;Ma, Joohyung;Hwang, Sun Hee;Song, Tongjin;Khang, Gon
    • Journal of the Korean Society for Precision Engineering
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    • v.32 no.10
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    • pp.845-850
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    • 2015
  • This study was designed to investigate the feasibility of utilizing an adaptation for selective elicitation of tactile sensations by means of transcutaneous electrical stimulation. We conducted the first experiment to investigate how the stimulation frequency affected the adaptation. Twenty healthy subjects participated in the second experiment to confirm our proposal that the perception intensity of the low-frequency vibration can be enhanced after a high-frequency adaptation, and vice versa. It was found that (1) a low-frequency stimulation did not adapt the nerve afferents responsible for the high-frequency vibration, (2) a high-frequency stimulation affected the nerve afferents responsible for the low-frequency vibration, but adapted to the pressure sensation more intensely, and (3) more than 62% of the subjects reported a more clear selective sensation after the adaptation had lessened or depressed the unwanted sensation. The observations showed that adaptation of the nerve afferent could be utilized for selective elicitation of tactile sensations.

Advanced Computational Dissipative Structural Acoustics and Fluid-Structure Interaction in Low-and Medium-Frequency Domains. Reduced-Order Models and Uncertainty Quantification

  • Ohayon, R.;Soize, C.
    • International Journal of Aeronautical and Space Sciences
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    • v.13 no.2
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    • pp.127-153
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    • 2012
  • This paper presents an advanced computational method for the prediction of the responses in the frequency domain of general linear dissipative structural-acoustic and fluid-structure systems, in the low-and medium-frequency domains and this includes uncertainty quantification. The system under consideration is constituted of a deformable dissipative structure that is coupled with an internal dissipative acoustic fluid. This includes wall acoustic impedances and it is surrounded by an infinite acoustic fluid. The system is submitted to given internal and external acoustic sources and to the prescribed mechanical forces. An efficient reduced-order computational model is constructed by using a finite element discretization for the structure and an internal acoustic fluid. The external acoustic fluid is treated by using an appropriate boundary element method in the frequency domain. All the required modeling aspects for the analysis of the medium-frequency domain have been introduced namely, a viscoelastic behavior for the structure, an appropriate dissipative model for the internal acoustic fluid that includes wall acoustic impedance and a model of uncertainty in particular for the modeling errors. This advanced computational formulation, corresponding to new extensions and complements with respect to the state-of-the-art are well adapted for the development of a new generation of software, in particular for parallel computers.