• Title/Summary/Keyword: Nonlinear modulation

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All Digital GMSK Modulator for the GSM Mobile System (GSM 무선통신 시스템을 위한 디지털 GMSK 변조기 설계 및 성능분석)

  • 김범진;한재충;홍승억
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.25 no.4A
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    • pp.502-511
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    • 2000
  • The Gaussian Minimum Shift Keying (GMSK) modulation technique belongs to the class of nonlinear modulation technique, and it is known to be bandwidth efficient. The GMSK modulation is chosen for the digital cellular phone standard by the European Telecommunications Standards Institute (ETSI). In this paper, an efficient method for implementing all digital GMSK modulator is introduced. The proposed modulator is shown to be simple to implement as well as satisfying the required spectral shape recommended by the ETSI.

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Research about ESPI System Algorithm Development that Use Modulating Laser (Modulating Laser를 이용한 ESPI System algorithm 개발에 관한 연구)

  • Kim, Seong-Jong;Kang, Young-June;Park, Nak-Kyu;Lee, Dong-Hwan
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.7
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    • pp.65-72
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    • 2009
  • Laser interferometry is widely used as a measuring system in many fields because of its high resolution and its ability to measure a broad area in real-time all at once. In conventional laser interferometry, for example out-of-plane ESPI (Electronic Speckle Pattern Interferometry), in plane ESPI, shearography and holography, it uses PZT or other components as a phase shift instrumentation to extract 3-D deformation data, vibration mode and others. However, in most cases PZT has some disadvantages, which include nonlinear errors and limited time of use. In the present study, a new type of laser interferometry using a laser diode is proposed. Using Laser Diode Sinusoidal Phase Modulating (LD-SPM) interferometry, the phase modulation can be directly modulated by controlling the laser diode injection current thereby eliminating the need for PZT and its components. This makes the interferometry more compact. This paper reports on a new approach to the LD (Laser Diode) Modulating interferometry that involves four-frame phase shift method. This study proposes a four-frame phase mapping algorithm, which was developed to have a guaranteed application, to stabilize the system in the field and to be a user-friendly GUI. In this paper, the theory for LD wavelength modulation and sinusoidal phase modulation of LD modulating interferometry is shown. Using modulating laser and research of measurement algorithm does comparison with existent ESPI measurement algorithm. Algorithm measures using GPIB communication through most LabVIEW 8.2. GPIB communication does alteration through PC. Transformation of measurement object measures through modulating laser algorithm that develops. Comparison of algorithm of modulating laser developed newly with existent PZT algorithm compares transformation price through 3-D. Comparison of 4-frame phase mapping, unwrapping, 3-D is then introduced.

Performance of 8SQAM System in a Nonlinearly Amplified Channel Environment (비선형 증폭 채널 환경에서 8SQAM 시스템의 성능)

  • 성봉훈;서종수
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.7C
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    • pp.669-677
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    • 2003
  • A new Modem technique - 8SQAM(8-state Superposed Quadrature Amplitude Modulation) - for use in power and bandwidth limited digital communication system is proposed. 8SQAM is free of inter-symbol interference(ISI) and generates output signals which have a smooth and continuous phase transition and a reduced envelope fluctuation by keeping correlation between amplitudes and phases of two subsequent symbols. Accordingly, 8SQAM, as compared with a conventional 8PSK, is influenced a little by ISI and inter-modulation(IM) caused by nonlinear distortions. In this paper, the performance of the 8SQAM system, in a nonlinearly amplified channel impaired by additive white Gaussian noise(AWGN), ISI and IM, is analyzed via computer simulation. The simulation result shows that 8SQAM outperforms 8PSK with roll-off value of $\alpha$=0.25 by 2.5dB in CNR to maintain BER=1$\times$10$^{-4}$ when input back-off(IBO) of HPA is 3dB.

Phase Noise Analysis in the OFDM Communication System (OFDM 통신시스템에서 위상 잡음분석)

  • 이영선;유흥균;정영호;함영권
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.11
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    • pp.1043-1050
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    • 2004
  • In this paper, Phase noise is analyzed and a novel approach of the nonlinear approximation including second order term of phase noise is presented to analyze and quantize system performance. As results, in QPSK-OFDM system, when PLL loop bandwidth is 5.0 Hz, 1.0 kHB, 0.5 kHz respectively, there are about 0.6 dB, 1.0 dB, 1.7 dB SNR penalties at BER=10$\^$-4/ compared with system without phase noise in AWGN channel. In 16QAM modulation, there are about 1.9 dB, 3.2 dB, 6.7 dB SNR penalties at BER=10$\^$-4/ respectively. At QPSK-OFDM system, comparing the previous linear approximation method with our proposed nonlinear approximation method, there is similar BER performance at phase noise variance lower than 0.02, but certain difference occurs as variance increases more than 0.02. Furthermore, analytical BER results closely match with simulation results in the OFDM system employing QPSK and 16qAM modulation. And, BER performance of QPSK-OFDM system is considerably degraded because of the BER error floor if the phase noise variance becomes larger than 0.03.

SER Analysis of Arbitrary Two-Dimensional Signaling over Nonlinear AWGN Channels (비선형 채널에서 임의의 2차원 변조 신호의 SER 분석)

  • Lee, Jae-Yoon;Yoon, Dong-Weon;Cho, Kyong-Kuk
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.7A
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    • pp.738-745
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    • 2007
  • The non-linearity of HPA(high power amplifier) which is an important component in modern communications systems introduces AM/AM and AM/PM distortion so that the transmitted signal is deteriorated. And, the I/Q unbalances and phase error which are generated by non-ideal components are inevitable physical phenomena and lead to performance degradation when we implement a practical two-dimensional (2-D) modulation system. In this paper, we provide an exact and general expression involving the 2-D Gaussian Q-function for the error probabilities of arbitrary 2-D signaling with I/Q amplitude and phase unbalances in nonlinear additive white Gaussian noise (AWGN) channels by using the coordinate rotation and shifting technique.

The Characteristic Improvement of Inverter Output for Static UPS (UPS용 인버터 출력특성 개선)

  • Kim, D.U.;Kim, Y.P.;Shin, H.J.;Baek, B.S.;Ryu, S.P.;Min, B.G.
    • Proceedings of the KIEE Conference
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    • 1998.07f
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    • pp.2051-2053
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    • 1998
  • In spite of nonlinear or step-changing load and line disturbances, the inverter for the UPS must provide the pure sinusoidal output voltage with low THD(Total Harmonics Distortion). This paper proposes an inverter controller for the UPS which has a good dynamic response characteristic and robustness for applying industrial world directly. The inverter output voltage is controlled instantaneously with a double regulation loop by a TMS320C31 Digital Signal Processor so that it has very good dynamic response for nonlinear or step-changing load and line disturbances. To improve the voltage utilization and response characteristics, the Space Vector Modulation(SVM) technique is adapted for the switching method of this system. The characteristics of the proposed control system were verified by simulations and experiments.

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Closed-loop Identification and Controller Design for a Converter (컨버터의 폐루프 식별 및 제어기 설계)

  • Yun, Kyong-Han;Lim, Yeon-Soo;Jin, Li-Hua;Kim, Jae-Jin;Kim, Young-Chol
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1632-1633
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    • 2007
  • This paper presents a new method of designing digital controller based on closed-loop identification of a pulse width modulation (PWM) converter system. We consider the control system structure which is composed of both current control loop and voltage control loop. The current controller can be designed independently of voltage loop. Whereas voltage controller can not do easily due to the PWM switching component which is nonlinear in nature. Furthermore, the control objective of inner loop is to track the sine wave of 60 Hz, but the outer loop shall maintain the constant DC voltage irrespective to load change. To systematically design outer loop controller, we propose a method finding linear approximate model of the nonlinear inner loop part including current controller by closed loop identification. Based on the identified model, we show that a simple digital voltage controller can be directly designed and it has good performance.

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Augmentation of Fractional-Order PI Controller with Nonlinear Error-Modulator for Enhancing Robustness of DC-DC Boost Converters

  • Saleem, Omer;Rizwan, Mohsin;Khizar, Ahmad;Ahmad, Muaaz
    • Journal of Power Electronics
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    • v.19 no.4
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    • pp.835-845
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    • 2019
  • This paper presents a robust-optimal control strategy to improve the output-voltage error-tracking and control capability of a DC-DC boost converter. The proposed strategy employs an optimized Fractional-order Proportional-Integral (FoPI) controller that serves to eliminate oscillations, overshoots, undershoots and steady-state fluctuations. In order to significantly improve the error convergence-rate during a transient response, the FoPI controller is augmented with a pre-stage nonlinear error-modulator. The modulator combines the variations in the error and error-derivative via the signed-distance method. Then it feeds the aggregated-signal to a smooth sigmoidal control surface constituting an optimized hyperbolic secant function. The error-derivative is evaluated by measuring the output-capacitor current in order to compensate the hysteresis effect rendered by the parasitic impedances. The resulting modulated-signal is fed to the FoPI controller. The fixed controller parameters are meta-heuristically selected via a Particle-Swarm-Optimization (PSO) algorithm. The proposed control scheme exhibits rapid transits with improved damping in its response which aids in efficiently rejecting external disturbances such as load-transients and input-fluctuations. The superior robustness and time-optimality of the proposed control strategy is validated via experimental results.

Underwater Optical Image Data Transmission in the Presence of Turbulence and Attenuation

  • Ramavath Prasad Naik;Maaz Salman;Wan-Young Chung
    • Journal of the Institute of Convergence Signal Processing
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    • v.24 no.1
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    • pp.1-14
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    • 2023
  • Underwater images carry information that is useful in the fields of aquaculture, underwater military security, navigation, transportation, and so on. In this research, we transmitted an underwater image through various underwater mediums in the presence of underwater turbulence and beam attenuation effects using a high-speed visible optical carrier signal. The optical beam undergoes scintillation because of the turbulence and attenuation effects; therefore, distorted images were observed at the receiver end. To understand the behavior of the communication media, we obtained the bit error rate (BER) performance of the system with respect to the average signal-to-noise ratio (SNR). Also, the structural similarity index (SSI) and peak SNR (PSNR) metrics of the received image were evaluated. Based on the received images, we employed suitable nonlinear filters to recover the distorted images and enhance them further. The BER, SSI, and PSNR metrics of the specific nonlinear filters were also evaluated and compared with the unfiltered metrics. These metrics were evaluated using the on-off keying and binary phase-shift keying modulation techniques for the 50-m and 100-m links for beam attenuation resulting from pure seawater, clear ocean water, and coastal ocean water mediums.

Reduction of Structural and Computational Complexity in IMD Reduction Method of the PTS-based OFDM Communication System (PTS 방식의 OFDM 통신 시스템에서 IMD 저감 기법의 복잡도와 계산량 저감)

  • Kim, Seon-Ae;Lee, Il-Jin;Baek, Gwang-Hoon;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.8A
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    • pp.583-591
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    • 2009
  • OFDM(orthogonal frequency division multiplexing) signal with high PAPR(peak to average power ratio) produces the nonlinear distortion and/or decreases down the power efficiency of HPA(high power amplifier). So, the IMD(inter-modulation distortion) reduction method was proposed to reduce the nonlinear distortion, which shows better BER(bit error rate) performance than the PAPR reduction methods. However, IMD reduction method has inherent problem which system complexity and processing time increases because the FFT(fast Fourier transform) processor is added in transmitter and decision criterion of IMD reduction method is computed in frequency domain,. In this paper, therefore, we propose a new IMD reduction method to reduce the computational complexity and structure of IMD computation. And we apply this proposed method into OFDM system using PTS(partial transmit sequence) scheme and compare the computational complexity between conventional and proposed IMD reduction method. This method can reduce the system size and computational complexity. Also, the proposed has almost same BER performance with the conventional IMD reduction method.