• Title/Summary/Keyword: reference frequency transmission

Search Result 77, Processing Time 0.033 seconds

Accuracy of Free Space Path Loss and Matched Filter Gain Approximated by Using Passband Rectangular Pulse for Ultra Wideband Radio Systems

  • Supanakoon, Pichaya;Tanchotikul, Suchada;Tangtisanon, Prakit;Promwong, Sathaporn;Takada, Jun-Ichi
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 2004.08a
    • /
    • pp.223-226
    • /
    • 2004
  • This paper analyzes the accuracy of free space path loss and matched filter gain approximated by using a passband rectangular pulse for ultra wideband (UWB) radio systems. The example causal signal, a modulated Gaussian pulse with the same center frequency and frequency bandwidth of the passband rectangular pulse, is used to consider the accuracy. The path loss and matched filter gain of the modulated Gaussian pulse are simulated for the reference results. The UWB free space path loss is shown and is compared with that obtained from simulation and Friis' transmission formula. The UWB matched filter gain is shown and compared with simulation results. From the results, we can see that the UWB path loss formula is more accurate than the Friis' transmission formula. The results from the UWB free space path loss and matched filter gain formulas agree with the simulation. Then, these free space path loss and matched filter gain formulas approximated by using a passband rectangular pulse are appropriate for UWB system.

  • PDF

Vibration Analysis of Damper System in Torque Converter (토크 컨버터의 댐퍼 진동 특성)

  • Park, Tae-Jun;Kim, Myung-Sik;Jang, Jae-Duk;Joo, In-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2007.05a
    • /
    • pp.305-310
    • /
    • 2007
  • This paper presents a damper system design in torque converter to minimize the vibration in powertrain of automatic transmission vehicle. The lock-up clutch in torque converter makes engine and transmission connected directly. When the lock-up clutch is engaged the torque fluctuation of engine is attenuated by the damper system. This function decides the vehicle power-train dynamic characteristics. At first, the dynamic hysteresis effect with any self and surface to surface contact problems of the damper springs in the damper system for torque converter is analyzed by using FEM. It is shown that these simulation results have a good design reference to energy dissipation operating by damper system in torque converter. And, to calculate dynamic characteristics, the vehicle model is structured by using $AMESim^{(R)}$?? that is a common use program. The vehicle model shows the frequency response of vehicle by changing the stiffness of damper spring, and these results lead the most suitable stiffness of spring. Also, new damper system is analyzed resonance frequency variation and is compared with prior damper.

  • PDF

Hydraulic Constant Frequency Generation System Driven by Main Engine for Small Fishing Boat - Hydraulic Pump Control Type - (소형 어선용 주기구동 유압식 고주파수 발전장치에 관한 연구 ( 1 ) - 유압펌프 제어방식 -)

  • Lee, Il-Yeong;Park, Sang-Gil;Jeong, Yong-Gil
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.24 no.1
    • /
    • pp.30-35
    • /
    • 1988
  • An electrical power generation system driven by main engine shaft, briefly SG system for middle or small size fishing boat is studied experimently. In the SG system, power transmission is performed by a variable displacement hydraulic pump driven by the main engine and a constant displacement hydraulic motor. It was verified that the SG system enabled the generation of electrical power with constant frequency regardless main engine speed. In the SG system, setting reference frequency, sensing generator output frequency and setting controller parameters are performed by performed by programming in a microcomputer, so a countermeasure for physical situations of control object is very easy. Futhermore, the SG system has following features; low initial installation cost, wide freedom of installation in engine room, advantage of application in existing ships, especially fishing boat with hydraulic fishing equipments.

  • PDF

An Analysis of the Sound Transmission through a Plate Installed inside an Impedance Tube (임피던스 튜브 내에 설치된 평판의 음파투과해석)

  • Kim, Hyun-Sil;Kim, Bong-Ki;Kim, Sang-Ryul;Lee, Seong-Hyun
    • The Journal of the Acoustical Society of Korea
    • /
    • v.34 no.3
    • /
    • pp.219-226
    • /
    • 2015
  • In this paper, derivation of the STL (Sound Transmission Loss) of a square plate installed in an impedance tube is discussed using an analytic method. Coupled motion of the plate vibration and acoustic field is considered. Vibration of the plate and pressure field inside the tube are expressed in terms of the infinite series of modal functions. Under the plane wave assumption, it is shown that consideration of the first few modes yields sufficiently accurate results. When the boundary of the plate is clamped, vibration mode is assumed as a multiplication of the beam modes corresponding to the crosswise directions. The natural frequencies of the clamped plate are calculated using the Rayleigh-Ritz method. It is found that the STL shows a dip at the lowest natural frequency of the plate, and increases as the frequency decreases below the natural frequency. Comparison of the result in this paper with the STL obtained by measurements and FE computations in the reference shows an excellent agreement.

A performance analysis of the discrete time DS/CDMA system based on the code phase difference (코드 위상차에 따른 이산 시간 CDMA 시스템의 성능 분석)

  • 안병양
    • Journal of the Korean Institute of Telematics and Electronics S
    • /
    • v.35S no.5
    • /
    • pp.11-16
    • /
    • 1998
  • DS/CDMA systems for the high speed communication require high code rats. In discrete time CDMA receivers, the performance degradation, caused by the phase difference between transmission code and reference code, increase the sampling frquency of the receiver. This increment of the sampling frequency makes hard to implement high speed CDMA systems. This paper analyzes the SIR(signal to interference Ratio) performance of the discrete time DS/CDMA system, based on the code phase difference. The results of this paper may be useful to study a low-sampling CDMA receiver.

  • PDF

Damping and Transmission Loss of Polyurethane Multi-Layer (폴리우레탄 다층구조의 감치 및 투과손실)

  • Lee Yong Geon;Lim Yi Rang;Kwon Oh Hyeong;Yoon Kwan Han
    • Polymer(Korea)
    • /
    • v.29 no.3
    • /
    • pp.300-303
    • /
    • 2005
  • Polyurethane multi-layer and foam multi-layer were prepared with PU1000 and PU2000 made by poly(propylene glycol) (PPG) having the molecular weight of 1000 and 2000 g/mol, respectively. The damping and transmission loss of these materials were compared with PU1000 used as a reference. The damping peak of polyurethane multi-layer was shifted to the lower temperature compared with PU1000, while the damping peak of polyurethane foam multi-layer was shifted to the higher temperature and broaden. In terms of noise reduction, the transmission loss of polyurethane multi-layer was effective at the specific frequency range such as less than 100 Hz and around 600 Hz compared with PU1000. The transmission loss of polyurethane foam multi-layer was most effective in the whole experimental frequency range.

Optimal Design of a Muffler with Perforated Plates Considering Pressure Drop (압력 강하를 고려한 머플러 천공판 최적설계)

  • Choi, Dong Wook;Lee, Jin Woo
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.23 no.4
    • /
    • pp.372-378
    • /
    • 2013
  • An acoustical shape optimization problem is formulated for optimal design of a perforated reactive muffler with offset inlet/outlet. The mean transmission loss value in a target frequency range is maximized for an allowed pressure drop value between an inlet and an outlet. Partitions in the chamber are divided into several sub-partitions, whose lengths are selected as design variables. Each sub-partition has the same number of holes, whose sizes are equal. A finite element model is employed for acoustical and flow analyses. A gradient-based optimization algorithm is used to obtain an optimal muffler. The acoustical and fluidic characteristics of the optimal muffler are compared with those of a reference muffler. Validation experiment is carried out to support the effectiveness of our suggested method.

Control Strategy of MMC-HVDC under Unbalanced Grid Voltage Conditions

  • Zhang, Jianpo;Zhao, Chengyong
    • Journal of Power Electronics
    • /
    • v.15 no.6
    • /
    • pp.1499-1507
    • /
    • 2015
  • High voltage direct current transmission based on modular multilevel converter (MMC-HVDC) is one of the most promising power transmission technologies. In this study, the mathematical characteristics of MMC-HVDC are analyzed in a synchronous rotational reference frame. A hybrid current vector controller based on proportional integer plus resonant is used to uniformly control the DC and double-base frequency AC currents under unbalanced grid voltage conditions. A corresponding voltage dependent current order limiter is then designed to solve the overcurrent problems that may occur. Moreover, the circulating current sequence components are thoroughly examined and controlled using a developed circulating current suppressor. Simulation results verify the correctness and effectiveness of the proposed control schemes.

Implementation of Coupler for Live Wire Fault Detection System using Time-Frequnecy Domain Reflectometry (커플러를 이용한 활선 상태 배선 진단 시간-주파수 영역 반사파 계측 시스템 구현)

  • Doo, Seung-Ho;Kwak, Ki-Seok;Yoon, Tae-Sung;Park, Jin-Bae
    • Proceedings of the KIEE Conference
    • /
    • 2008.07a
    • /
    • pp.1541-1542
    • /
    • 2008
  • In this paper, we introduce a live wire power transmission line fault detection system using time-frequency domain reflectometry(TFDR). The TFDR is known that is more precise method than the other conventional ones. However, the TFDR is generally adopted only in fault detection for communication cable, and dead line power transmission line. Therefore, this paper suggests a TFDR system with coupler which separates 220V, 60Hz signal and TFDR reference signal for implementation the live wire fault detection system. This approach is verified by circuit simulation.

  • PDF

Side Information Transmission using Reference Symbol in PTS Scheme (PTS 방식에서 기준 심볼을 이용한 부가정보 전송)

  • 유흥균;박종현;박진수
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
    • /
    • v.15 no.4
    • /
    • pp.414-420
    • /
    • 2004
  • Partial transmit sequence(PTS) scheme has been widely studied to reduce the peak-to-average power ratio(PAPR) of Orthogonal frequency-division multiplexing(OFDM) signal since it is flexible ad any spectral regrowth is not made. A necessity of the PTS scheme is to transmit the side information about the phase rotation factors for correct OFDM symbol recovery. In this paper, a new side information embedded PTS scheme using the reference symbols is proposed fur the PAPR reduction and the BER(bit error rate) performance is analyzed when the erroneous side information is received. In this proposed method, the information about the rotation factors is expressed by the phase of reference symbols. The proposed method maintains the same PAPR reduction performance as the conventional PTS scheme and OFDM symbols are correctly recovered by the side information to meet the required BER level, which is verified via the computer simulation. Also, it is shown that the proposed method can be easily realized and can be used for all kinds of digital modulation formats in the OFDM communication system.