• Title/Summary/Keyword: Modulation

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Constant-Amplitude Multi-Code Trans-Orthogonal Modulation (정진폭 다중부호 트랜스직교변조)

  • Hong, Dae-Ki
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.1
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    • pp.493-499
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    • 2011
  • To improve the bandwidth efficiency of conventional orthogonal modulation, the MCTO(Multi-Code Trans-Orthogonal) modulation, which is modified orthogonal modulation, was proposed. However, the RF(Radio Frequency) power amplifier for the MCTO modulation is too complex to reject the amplitude distortion due to the non-constant amplitude property of the MCTO. Therefore, in this paper, CAMCTO(constant-amplitude multi-code trans-orthogonal) modulation is proposed by using the constant-amplitude encoding algorithm for multi-code signal. Additionally, the performance of the proposed CAMCTO modulation is compared with those of the orthogonal modulation and the MCTO modulation by using the computer simulation. The computer simulations show that the bandwidth efficiency of the proposed CAMCTO modulation is better than that of the conventional orthogonal modulation.

Research on the Robust Modulation for the reception improvement of VSB System in dynamic multipath channel (동적다중경로 채널에서 VSB시스템의 수신성능개선을 위한 강인한 변조기법 연구)

  • 배재휘;서재현;김승원
    • Proceedings of the IEEK Conference
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    • pp.13-16
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    • 2002
  • This paper presents a new baseband modulation system for the reception improvement of VSB system in dynamic multipath channel. By introducing the 1/2 Trellis Coded Modulation in baseband modulation, the TOV of proposed modulation is improved very much compared with 8-VSB modulation and better than the pseudo 2-VSB modulation of Philips which is the most robust modulation for VSB transmission system as far. Through the computer simulation, the performance of the proposed modulation is examined and the results are shown.

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Analysis and Implementation of Multiphase Multilevel Hybrid Single Carrier Sinusoidal Modulation

  • Govindaraju, C.;Baskaran, K.
    • Journal of Power Electronics
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    • v.10 no.4
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    • pp.365-373
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    • 2010
  • This paper proposes a hybrid single carrier sinusoidal modulation suitable for multiphase multilevel inverters. Multiphase multilevel inverters are controlled by hybrid modulation to provide multiphase variable voltage and a variable frequency supply. The proposed modulation combines the benefits of fundamental frequency modulation and single carrier sinusoidal modulation (SC-SPWM) strategies. The main characteristics of hybrid modulation are a reduction in switching losses and improved harmonic performance. The proposed algorithm can be applied to cascaded multilevel inverter topologies. It has low computational complexity and it is suitable for hardware implementations. SC-SPWM and its base modulation design are implemented on a TMS320F2407 digital signal processor (DSP). A Complex Programmable Logic Device realizes the hybrid PWM algorithm and it is integrated with a DSP processor for hybrid SC-SPWM generation. The feasibility of this hybrid modulation is verified by spectral analysis, power loss analysis, simulation and experimental results.

A Simplified Carrier-Based Pulse-Width Modulation Strategy for Two-level Voltage Source Inverters in the Over-modulation Region

  • Jing, Feng;He, Feng-You
    • Journal of Power Electronics
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    • v.17 no.6
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    • pp.1480-1489
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    • 2017
  • In this study, a carrier-based pulse-width modulation (PWM) method for two-level voltage source inverters in the over-modulation region is proposed. Based on the superposition principle, the reference voltage vectors outside the linear modulation boundary are adjusted to relocate to the vector hexagon, while their fundamental magnitudes are retained. In accordance with the adjusted reference vector, the corresponding modulated waves are respectively deduced in over-modulation mode I and II to generate the gate signals of the power switches, guaranteeing the linearity of the fundamental output phase voltage in the over-modulation region. Moreover, due to the linear relationship between the voltage vector and the duty ratios, the complicated sector identification and holding angle calculation found in previous methods are avoided in the modulated wave synthesis, which provides great simplicity for the proposed carrier-based over-modulation strategy. Experimental results demonstrate the effectiveness and validity of the proposed method.

The Optimal Condition for Velocity Modulation

  • Park, Joon-Suk;Kim, Do-Nyun
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1157-1159
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    • 2003
  • The effect of the scan velocity modulation is studied. The effect of the velocity modulation on the picture image is judged from the intensity profile of the image. The intensity profile is obtained as time integral of moving Gaussian beam. To confirm the applicability of this integral formula, the measurement and simulation data is compared. And by calculating the intensity profile for different amounts of velocity modulation, the optimum modulation displacement that gives the best image quality is obtained. This optimum modulation displacement can be used in designing scan velocity modulation system.

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Analysis of Output Characteristics for the Resonant DC Link Inverter Using PWM Inverter Modulation Methods (인버터 PWM 방식을 이용한 공진형 직류 링크 인버터의 출력 특성 해석)

  • 김윤호;윤병도;이병순
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.41 no.6
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    • pp.615-624
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    • 1992
  • For the operation of the resonant DC link inverters, only limited number of modulation techniques such as the delta modulation and instantaneous current control techniques have been suggested. However, these modulation techniques have some limitations in practical operation. In this paper, the application of conventional inverter modulation techniques is suggested for the control of the resonant DC link inverter. The harmonic analysis results are presented. The results show that these modulation techniques offer good output characteristics similar to conventional inverter PWM techniques for the operation of the resonant DC link inverter. This implies that not only the delta modulation technique and instantaneous current control techniques but also various other modulation techniques can be applied to the operation of the resonant DC link inverter. This also indicates that open loop control as well as closed loop control can be used for the operation of the resonant inverter. The resonant DC link inverter with various modulation strategies is implemented using V-40 microprocessors.

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SVPWM Overmodulation Scheme of Three-Level Inverters for Vector Controlled Induction Motor Drives

  • Kwon, Kyoung-Min;Lee, Jae-Moon;Lee, Jin-Mok;Choi, Jae-Ho
    • Journal of Power Electronics
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    • v.9 no.3
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    • pp.481-490
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    • 2009
  • This paper describes a SVPWM overmodulation scheme of NPC type three-level inverter for traction drives which extends the modulation index from MI=0.907 to unity. SVPWM strategy is organized by two operation modes of under-modulation and over-modulation. The switching states under the under-modulation modes are determined by dividing them with two linear regions and one hybrid region the same as the conventional three-level inverter. On the other hand, under the over-modulation mode, they are generated by doing it with two over-modulation regions the same as the conventional over-modulation strategy of a two level inverter. Following the description of over-modulation scheme of a three-level inverter, the system description of a vector controlled induction motor for traction drives has been discussed. Finally, the validity of the proposed modulation algorithm has been verified through simulation and experimental results.

Constant-Amplitude Biorthogonal Multi-Code Modulation (정 진폭 다중 보호 이진 직교 변조)

  • Hong Dae ki;Kang Sung jin;Ju Min chul;Kim Young sung;Seo Kyeung hak;Cho Jin woong
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.3C
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    • pp.69-76
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    • 2005
  • In this paper, we propose a biorthogonal modulation employing a constant-amplitude transmission of multi-code signals by introducing a simple constant-amplitude coding scheme with redundant bits. The proposed constant-amplitude biorthogonal multi-code (CABM) modulation can provide high spectral efficiency compared with a conventional direct sequence/spread spectrum (DS/SS) modulation. Nevertheless the proposed CABM modulation can keep up a constant-amplitude signal. Additionally, we propose various types of demodulation structures for the CABM modulation. Simulation results show that bit error rate (BER) performance and hardware complexity of the proposed CABM modulation are highly improved in comparison with those of a constant-amplitude orthogonal multi-code (CAOM) modulation.

Frequency modulation of a waveguide cavity cw IMPATT diode oscillator (도파관캐비티를 사용한 임팻다이오드 발진기의 주파수변조특성)

  • 윤현보
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.12 no.6
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    • pp.1-4
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    • 1975
  • This paper dells with the impedance variations of the IMPATT diode depending upon the small a.c. coomponent superimposed on the d.c. bias. The frequency deviation of the modulated wave is measured using a carrier null method on microwave spectrum analyser. Frequency modulation is achieved by the weack a.c. signal superimposed on the d.c. bias. The bandwidth rapidly increase with increasing modulation signal magnitude for constant modulation frquency and slightly decrease with decreasing modulation frequency for constant modulation signal magnitude.

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