• 제목/요약/키워드: Nonlinear phase

검색결과 1,080건 처리시간 0.022초

Time- and Frequency-Domain Optimization of Sparse Multisine Coefficients for Nonlinear Amplifier Characterization

  • Park, Youngcheol;Yoon, Hoijin
    • Journal of electromagnetic engineering and science
    • /
    • 제15권1호
    • /
    • pp.53-58
    • /
    • 2015
  • For the testing of nonlinear power amplifiers, this paper suggests an approach to design optimized multisine signals that could be substituted for the original modulated signal. In the design of multisines, complex coefficients should be determined to mimic the target signal as much as possible, but very few methods have been adopted as general solutions to the coefficients. Furthermore, no solid method for the phase of coefficients has been proven to show the best resemblance to the original. Therefore, in order to determine the phase of multisine coefficients, a time-domain nonlinear optimization method is suggested. A frequency-domain-method based on the spectral response of the target signal is also suggested for the magnitude of the coefficients. For the verification, multisine signals are designed to emulate the LTE downlink signal of 10 MHz bandwidth and are used to test a nonlinear amplifier at 1.9 GHz. The suggested phase-optimized multisine had a lower normalized error by 0.163 dB when N = 100, and the measurement results showed that the suggested multisine achieved more accurate adjacent-channel leakage ratio (ACLR) estimation by as much as 12 dB compared to that of the conventional iterative method.

Adelphic Integral을 이용한 비선형 정규모드 진동 해석 (A Study on the Nonlinear Normal Mode Vibration Using Adelphic Integral)

  • Huinam Rhee;Joo, Jae-Man;Pak, Chol-Hui
    • 한국소음진동공학회:학술대회논문집
    • /
    • 한국소음진동공학회 2001년도 추계학술대회논문집 II
    • /
    • pp.799-804
    • /
    • 2001
  • Nonlinear normal mode (NNM) vibration, in a nonlinear dual mass Hamiltonian system, which has 6th order homogeneous polynomial as a nonlinear term, is studied in this paper. The existence, bifurcation, and the orbital stability of periodic motions are to be studied in the phase space. In order to find the analytic expression of the invariant curves in the Poincare Map, which is a mapping of a phase trajectory onto 2 dimensional surface in 4 dimensional phase space, Whittaker's Adelphic Integral, instead of the direct integration of the equations of motion or the Birkhotf-Gustavson (B-G) canonical transformation, is derived for small value of energy. It is revealed that the integral of motion by Adelphic Integral is essentially consistent with the one obtained from the B-G transformation method. The resulting expression of the invariant curves can be used for analyzing the behavior of NNM vibration in the Poincare Map.

  • PDF

상호 위상 변조에 의해 왜곡된 WDM 신호의 Mid-Span Spectral Inversion을 이용한 보상 (Compensation of Distorted WDM signals due to Cross Phase Modulation Effects using Mid-Span Spectral Inversion)

  • 이성렬
    • 한국항행학회논문지
    • /
    • 제7권2호
    • /
    • pp.128-134
    • /
    • 2003
  • 광섬유의 색 분산과 자기 위상 변조 외에 상호 위상 변조 효과에 의해 왜곡된 WDM 채널 신호가 MSSI(Mid-Span Spectral Inversion) 기법을 통해 전송 거리에 따라 보상되는 정도를 다양한 광섬유 분산 계수를 고려하여 분석해 보았다. 본 연구에서 고려된 시스템은 전체 전송로의 중간에 비선형 매질로 HNL-DSF (Highly nonlinear dispersion shifted fiber)를 갖는 광 위상 공액기를 두고, 광 위상 공액기를 중심으로 첫 번째 전송 구간에서의 평균 강도와 두 번째 전송 구간에서의 평균 강도를 같게 하는 PAIA (Path Averaged Intensity Approximation) 방식의 MSSI 기법을 채택한 $3{\times}40$ Gbps 강도 변조 직접 검파 방식의 WDM 시스템이다. XPM에 의한 왜곡의 보상 측면에서 광섬유의 분산 계수가 비교적 큰 WDM 시스템일수록 MSSI 기법이 더욱 효과적으로 적용되어 전송 거리를 신장시킬 수 있는 것을 확인할 수 있었다. 또한 색 분산, SPM 외에 XPM의 영향을 받아 왜곡된 채널 신호는 MSSI 기법을 통해 광섬유의 분산 계수가 큰 시스템에서 더욱 안정되게 보상된다는 것을 알 수 있었다.

  • PDF

320 Gbps 강도 변조 직접 검파 WDM 시스템의 채널 보상에서 상호 위상 변조의 영향 (Effect of Cross Phase Modulation on Channel Compensation in 320 Gbps Intensity Modulation / Direct Detection WDM Transmission Systems)

  • 이성렬;김지웅;손성찬
    • 한국정보통신학회논문지
    • /
    • 제8권5호
    • /
    • pp.1134-1140
    • /
    • 2004
  • 320 Gbps WDM 시스템의 전송로에 색 분산과 자기 위상 변조 외에 상호 위상 변조 현상(XPM ; Cross Phase modulation)이 존재하는 경우 XPM 현상이 광 펄스 왜곡 보상에 미치는 영향을 광섬유분산 계수와 변조 파형 형식에 따라 분석해 보았다. 본 논문에서 고찰한 WDM 시스템은 전체 전송 링크 중간에 HNL-DSF (Highly Nonlinear Dispersion Shifted Fiber)를 비선형 매질로 이용한 광 위상 공액기를 두어 보상하는 MSSI (Mid-Span Spectral version) 기법에 기초를 두고 있다. MSSI가 적용 된다고 하더라도 WDM 채널간 XPM의 영향이 존재하면 전체적인 보상 정도가 감소하여 최대 전송 채널 전력의 크기가 광섬유 분산 계수에 관계하여 줄어드는 것을 확인할 수 있었고, WDM 시스템의 광섬유 분산 계수가 클수록 임의의 채널에 왜곡을 유도하는 XPM의 영향을 크게 감소시킬 수 있는 것을 알 수 있었다. 아울러 XPM의 영향을 최소화하기 위해 WDM 시스템에 분산 계수가 큰 광섬유를 사용하는 경우 전송 펄스 형식을 RZ보다 오히려 NRZ로 하게 되면 모든 채널을 매우 비슷한 정도로 보상할 수 있다는 것을 확인하였다.

슬라이딩모드를 이용한 자동변속기의 비선형제어 (Nonlinear Control of an Automatic Transmission Using Sliding Mode)

  • 조승호
    • 대한기계학회논문집
    • /
    • 제19권3호
    • /
    • pp.605-614
    • /
    • 1995
  • In the automatic transmission using planetary gear there exists nonlinearities due to the finite difference between gear ratios, which yield torque hole during shift and influence on the ride quality and life of clutch. Based on the reaction carrier and converter turbine speed sliding functions are defined. Nonlinear closed-loop control laws are derived using them. Computer simulation shows that the closed loop design is better than the open loop design and semi-closed loop design.

Nonlinear State Feedback for Minimum Phase in Nuclear Steam Generator Level Dynamics

  • Jeong, Seong-Uk;Choi, Jung-In
    • Journal of Electrical Engineering and information Science
    • /
    • 제2권3호
    • /
    • pp.66-70
    • /
    • 1997
  • The steam generator level is susceptible to the nonminimum phase in dynamics due to the thermal reverse effects known as "shrink and swell" in a pressurized water reactor. A state feedback assisted control concept is presented for the change of dynamic performance to the minimum phase the concept incorporates a nonlinear digital observer as a part of the control system. The observer is deviced to estimate the state variables that provide the true indication of water inventory by compensating for shrink and swell effects. The concept is validated with implementation into the steam generator simulation model.

  • PDF

HPA의 비선형 위상 왜곡을 고려한 타입기반 군 지연 등화기 (Type-Based Group Delay Equalizer Considering the Nonlinear Phase Distortion of HPA)

  • 김용국;조병각;백광훈;유흥균
    • 한국통신학회논문지
    • /
    • 제37A권10호
    • /
    • pp.895-902
    • /
    • 2012
  • 본 논문에서는 비선형 전력증폭기(PA:power amplifier)의 AM/PM 비선형 왜곡특성을 포함하는 군 지연을 보상하는 새로운 등화기를 제안한다. 군 지연 특성은 각 주파수 성분에 따라 서로 다르게 나타나는 상수가 아닌 비선형 시간지연이다. 전력증폭기에서 발생되는 AM/PM 특성으로 인한 위상 왜곡 현상은 군 지연을 증가시키는 주요한 요인이다. 이러한 군 지연 왜곡으로 신호 성상도에서 신호는 퍼지면서 회전하게 된다. 위와 같은 문제점을 고려하여 각 주파수 성분에 따라 다르게 나타나는 비선형 시간지연을 정적인 군지연으로 구분하고, PA의 AM/PM 특성인 입력신호 크기에 따라서 위상 천이가 다르게 발생하는 것을 동적인 군 지연으로 구분한다. 정적인 군 지연은 주파수 영역에서 Type-Based 방법으로 위상 왜곡을 추정 및 보상하고 동적인 군 지연은 시간영역에서 위상회전을 보상한다. 제안된 군 지연 보상기법으로 전력증폭기의 AM/PM 특성을 포함한 군 지연 특성을 충분히 보상할 수 있음을 확인하였다.

Nonlocal nonlinear dynamic behavior of composite piezo-magnetic beams using a refined higher-order beam theory

  • Fenjan, Raad M.;Ahmed, Ridha A.;Faleh, Nadhim M.
    • Steel and Composite Structures
    • /
    • 제35권4호
    • /
    • pp.545-554
    • /
    • 2020
  • The present paper explores nonlinear dynamical properties of piezo-magnetic beams based on a nonlocal refined higher-order beam formulation and piezoelectric phase effect. The piezoelectric phase increment may lead to improved vibrational behaviors for the smart beams subjected to magnetic fields and external harmonic excitation. Nonlinear governing equations of a nonlocal intelligent beam have been achieved based upon the refined beam model and a numerical provided has been introduced to calculate nonlinear vibrational curves. The present study indicates that variation in the volume fraction of piezoelectric ingredient has a substantial impact on vibrational behaviors of intelligent nanobeam under electrical and magnetic fields. Also, it can be seen that nonlinear free/forced vibrational behaviors of intelligent nanobeam have dependency on the magnitudes of induced electrical voltages, magnetic potential, stiffening elastic substrate and shear deformation.

Estimation of the Ratio of Nonlinear Optical Tensor Components by Measuring Second Harmonic Generation and Parametric Down Conversion Outputs in a Single Periodically Poled LiNbO3 Crystal

  • Kumar, CH. S.S. Pavan;Kim, Jiung;Kim, Byoung Joo;Cha, Myoungsik
    • Current Optics and Photonics
    • /
    • 제2권6호
    • /
    • pp.606-611
    • /
    • 2018
  • Measurement of the nonlinear optical coefficients is not an easy task since it requires complicated experimental setup and analysis. We suggest an easy way to estimate the relative nonlinear optical tensor components by direct measurement of the output powers of the second harmonic generation and spontaneous parametric down conversion experiments. The experiments were done in quasi-phase-matched type-0 as well as type-1 interactions at similar pump wavelengths in a 5% MgO-doped periodically poled $LiNbO_3$ crystal to obtain the ratio of the nonlinear optical tensor components $d_{33}/d_{31}$ in each experiment. The obtained ratios were then compared with the previously ascertained values [J. Opt. Soc. Am. B, 14, 2268-2294 (1997)].

Flow-induced instability and nonlinear dynamics of a tube array considering the effect of a clearance gap

  • Lai, Jiang;Sun, Lei;Li, Pengzhou
    • Nuclear Engineering and Technology
    • /
    • 제51권6호
    • /
    • pp.1650-1657
    • /
    • 2019
  • Fluidelastic instability and nonlinear dynamics of tube bundles is a key issue in a steam generator. Especially, once the post-instability motion of the tube becomes larger than the clearance gap to other tubes, effective contact or impact between the tubes under consideration and the other tube inevitable. There is seldom theoretical analysis to the nonlinear dynamic characteristics of a tube array in two-phase flow. In this paper, experimental and numerical studies were utilized to obtain the critical velocity of the flow-induced instability of a rotated triangular tube array. The calculation results agreed well with the experimental data. To explore the post-instability dynamics of the tube array system, a Runge-Kutta scheme was used to solve the nonlinear governing equations of tube motion. The numerical results indicated that, when the flow pitch velocity is larger than the critical velocity, the tube array system is undergoing a limit cycle motion, and the dynamic characteristics of the tube array are almost similar for different void fractions.