• Title/Summary/Keyword: Frequency modulation

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Performance of Channel Estimation in Two-Dimensional Modulation System

  • Nguyen, Quoc Kien;Jeon, Taehyun
    • International journal of advanced smart convergence
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    • v.9 no.3
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    • pp.137-140
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    • 2020
  • Orthogonal time frequency space (OTFS) modulation is considered as one of the solutions to cope with high mobility channel environments. It converts the time-varying channel to the near-constant channel response in the delay-Doppler domain. This modulation scheme also benefits from the diversity in two-dimensional modulation. According to recent researches, this method outperforms the conventional OFDM modulation, especially in high-speed channel conditions. In this paper, to investigate the performance of OTFS in a practical system, channel estimation in the delay-Doppler domain is compared with the conventional method in the time-frequency domain at different mobile speeds. Simulation results confirm that the delay-Doppler domain channel estimation brings a better performance compared to the conventional one under the same overhead rate.

A High Frequency Complex Modulation Method of the Electronic Ballast for Metal Halide Lamps (메탈 할라이드 램프용 전자식 안정기의 고주파 복합 변조법)

  • 오덕진;김희준;조규민
    • Journal of the Institute of Electronics Engineers of Korea SC
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    • v.40 no.3
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    • pp.215-224
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    • 2003
  • This paper presents an electronic ballast using a novel complex modulation method for the metal halide lamp. The proposed modulation method, which has a modulating signal of swept complex frequency, can eliminate the acoustic resonance more effectively than the conventional modulation method, which has a modulating signal of constant frequency. For the purpose of future application specific integrated circuits (ASIC). the controller of the proposed ballast has been designed only with erasable programmable logic devices (EPLDs), but without a microprocessor. In this paper, detailed proposed modulation schemes are described and experimental results on the proto type 150W metal halide lamp ballast with the proposed modulation method ate discussed.

Performance of Wavelet Packet Multicarrier Modulation Systems with Narrowband Interference (웨이블릿 패킷 다중반송파 변조 시스템의 협대역 간섭에 대한 성능)

  • Won, Yu-Jun;Seo, Bo-Seok
    • The Journal of the Korea Contents Association
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    • v.8 no.4
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    • pp.79-85
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    • 2008
  • These days, orthogonal frequency division multiplexing (OFDM) transmission method is widely used for broadband communication systems. The OFDM, which uses sine waves as orthogonal basis functions, is one of the orthogonal waveform modulation techniques. In this paper, we investigate a wavelet packet modulation method which uses wavelet packets instead of sine waves as the basis functions. The wavelet packets may have different patterns in two dimensional time-frequency domain, and we can design the packets appropriate for the channel environments with much flexibility. In this paper, we investigate the characteristics of the wavelet packet modulation as one of the multicarrier modulation methods, And we illustrate by simulations that narrowband interference can be reduced effectively by control the bandwidth of the wavelet packets.

Spray Characteristics of Modulated Liquid Jet Injected into a Subsonic Crossflow (주파수 변조 분사가 횡단 유동장의 분무 특성에 미치는 영향)

  • Lee, I.C.;Kim, J.H.;Koo, J.Y.
    • Journal of ILASS-Korea
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    • v.14 no.2
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    • pp.59-64
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    • 2009
  • These experiments are close examination of spray characteristics that are continuous liquid jet and modulated liquid jet. The experiments were conducted using water, over a range of crossflow velocities from $42{\sim}l36\;m/s$, with modulation frequencies of $35.7{\sim}166.2\;Hz$. Between continuous crossflow jet and modulated cross-flow jet of penetration, breakup point, spray angle and macro spray shape are experimentally investigated with image analysis. In cross-flow field, main parameter of liquid jet for breakup was cross-flow stream rather than modulation effect. As oscillation of the periodic pressure that could make liquid jet moved up and down, the mixing efficiency was increased. Also, a bulk of liquid jet puff was detected at upper field of liquid surface. So, this phenomenon has a good advantage of mixing spray from concentration of center area to outer area. Because of modulation frequency, SMD inclination of the structured layer was evanescent. Cross-sectional characteristics of SMD at downstream area were non-structured distributions. Then cross-sectional characteristics of SMD size were about same tendency over a range that is effect of spray mixing. The tendency of volume flux value for various modulation frequency was same distribution. And volume flux was decreased when the modulation frequency increase.

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A Study of Iterative Channel Estimation and Equalization Scheme of FBMC/OQAM in a Frequency Oversampling Domain (FBMC/OQAM 시스템의 주파수 과표본 영역에서의 반복적인 채널 추정 및 등화 기법에 관한 연구)

  • Won, YongJu;Oh, JongGyu;Lee, JinSeop;Kim, JoonTae
    • Journal of Broadcast Engineering
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    • v.21 no.3
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    • pp.391-403
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    • 2016
  • FBMC/OQAM(Filterbank multicarrier on offset-Quadrature Amplitude Modulation) system is a multicarrier modulation which is not need to use cyclic prefix(CP). The CP of OFDM/QAM (orthogonal frequency division multiplexing on Quadrature Amplitude Modulation) system decreases data transmission rate. However, SER(symbol error rate) performance of FBMC/OQAM system is worse than OFDM/QAM system with frequency 1-tap equalization scheme in the frequency selective channel. In this paper, an iterative channel estimation and equalization scheme is performed in a frequency oversampling domain about each sub-channel of FBMC/OQAM system and SER performance using computer simulation is shown. Using the proposed scheme, the SER performance approaches to that of OFDM/QAM system in a frequency selective channel.

The Listen-in Technique for Blind Signals (블라인드 신호 감청기술)

  • Nah, Sun-Phil;Park, Cheol-Sun;Jang, Won
    • Journal of the Korea Institute of Military Science and Technology
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    • v.8 no.4 s.23
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    • pp.102-109
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    • 2005
  • In this paper, we propose a new listen-in technique to overcome the problems and the shortcomings which could possibly meet in the previous listen-in methods to deal with the blind signal manually according to operator's decision. In the proposed listen-in method, receiving the signals, classifying the modulation types, and demodulating the signals can be done automatically without operator's intervention. We realize the listen-in technology by developing the high speed frequency tuner, the automatic modulation recognizer, and the signal demodulator. In conclusion, we confirm and show that the developed equipment has a good performance in classifying the modulation type through the computer simulation and the field test.

Circuit Design and Performance Analysis of CCFL Dimming Controller With Frequency Modulation

  • Kim, Cherl-Jin;Ji, Jae-Geun;Yoon, Shin-Yong
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.4B no.4
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    • pp.201-205
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    • 2004
  • The CCFL dimming control methods are generally used lamp current regulation or average current adjustment method feeding the CCFL inverter. Inverter operation frequency is higher than resonant frequency for safe operation. In this study, we design the half-bridge type series and parallel resonant converter circuit that switches at variable frequency modulation methods to control the output power. This method has advantages such as low EMI and reduced harmonics, and it is convenient for dimming control using a microprocessor. The validity of this study is confirmed from the simulation and experimental results.

Low Power Transmission Technique for Single-Carrier Modulation with Frequency Domain Equalization (주파수 영역 등화기를 사용하는 단일 반송파 전송 시스템을 위한 저 전력 전송 기법)

  • Jung, Hyeok Koo
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.66 no.4
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    • pp.247-251
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    • 2017
  • This paper proposes a low power transmission technique for single-carrier modulation with frequency domain equalization. As time domain signals and frequency domain signals have unique corresponding functions, inserting zeros after each symbol causes a repetition in other domain, so maximal ratio combining technique using repetitive transmission can be applied in the frequency domain. In this paper, we configure transmit signals to insert zeros after each symbols for single-carrier modulation with frequency domain equalization and maximal ratio receive combining block in the receiver structures, propose a structure for transmitter and receiver and show that its performance is better than the traditional algorithm by simulations.

Alternate Time-Switched Multiplexed Space-Frequency Block Coding technique for Single-Carrier System (단일 반송파 전송 시스템을 위한 교번 스위칭 다중화 공간 주파수 블록 코딩 기법)

  • Jung, Hyeok Koo
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.65 no.4
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    • pp.316-320
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    • 2016
  • This paper proposes an alternate time-switched multiplexed space-frequency block coding technique for single-carrier modulation with frequency domain equalization. The traditional multiplexed space-frequency block coding technique for single-carrier modulation uses multiple groups of two transmitters and suppresses the interference signals of other SFBC groups at the receiver. In this paper, we reconfigure transmit signals to adapt them for alternate time-switched multiplexed SFBC for single-carrier modulation with frequency domain equalization and receiver structures and propose a structure for transmitter and receiver, show that its performance is better than the traditional algorithm by simulations.

Study on Hybrid PWM Method under Low Switching Frequency

  • Kekang, Wei;Zheng, Trillion Q.;Wang, Ran;Wang, Chenchen
    • Journal of international Conference on Electrical Machines and Systems
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    • v.1 no.2
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    • pp.64-69
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    • 2012
  • This paper presents a hybrid pulse width modulation (PWM) method under low switching frequency conditions based on space vector PWM (SVPWM) and selective harmonic eliminated PWM (SHEPWM), which use asynchronous carrier modulation SVPWM at low frequency, and SHEPWM at high frequency, a square wave after rated conditions. A transitive strategy is proposed to realize a smooth transition of individual modes including SVPWM, SHEPWM and square waves. Experimental results confirm this hybrid modulation method and their transition are reasonable and proper.