• 한국정보통신학회논문지
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• 제5권2호
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• pp.289-296
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• 2001

본 논문에서는 뒤틀린 니매틱 액정디스플레이를 가변적인 위상마스크로 사용하여 기존의 2진 데이터 영상에 위상변조를 추가하는 방법을 제안한다 이를 위해 액정디스플레이의 위상변조특성을 이론 및 실험적으로 조사하였고, 입사빔 세기가 매우 커지면 위상변조 특성이 변하는 현상이 존재함을 실험적으로 보였다. 위상변조가 가미된 2진 데이터 영상의 저장특성을 실험적으로 조사하기 위해 여덟 장의 홀로그램을 각다중 을 사용해서 Dupont 사의 광폴리머의 한 지점에 기록하였다. 위상변조를 사용하여 Fourier 면 홀로그램을 기록할 경우, 기존의 진폭변조방식만 사용하는 경우에 비해 빔세기 균일도를 높일 수 있어서, 같은 조건에서 더 많은 홀로그램을 기록할 수 있음을 보였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2008년도 추계학술대회 논문집
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• pp.133-134
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• 2008

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.363-366
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• 2007

A new current control technique called Amplitude Shift Modulation (ASM) for cold cathode fluorescent lamps (CCFL) has been developed. This new technique sets and continuously controls the current of each individual CCFL in an LCD backlight lamp array.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 춘계학술대회 논문집
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• pp.90-95
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• 1995

This paper describes the highly-sensitive Si magnetic sensor using the amplitude modulation in order to real ice the integrated magnetic sensor which to sensor a weak magnetic field. Generally, the most important two parameters in Hall IC which degrade the ability of magnetic detection are the variation of offset according to the variation of temperature and the noise of amplifiers. In this paper, we use a Hall element and compensator to reduce the offset and the nouse of amplifiers by Using amplititude modulation method.

• 한국통신학회논문지
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• 제32권12A호
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• pp.1244-1250
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• 2007

무선 통신 시스템에서 사용자간 협력방식은 중계노드들이 송신노드로부터 수신한 정보를 전달해 주어 최종 수신신호의 신뢰도를 향상시킨다. 본 논문에서는, 독립적이고 동일하게 분포된 레일레이 페이딩 채널을 고려하여 사용자간 협력을 위한 디코딩 후 전달 중계방식에 대한 비트 오차율의 분석을 수행한다. 변조방식으로는 M-ary PAM (Pulse Amplitude Modulation), QAM (Quadrature Amplitude Modulation), PSK (Phase Shift Keying) 방식을 이용한다. 따라서, 주어진 중계노드의 수에 대하여 각 변조방식에 대한 비트 오차율 식을 유도한다. 최종적으로, 유도된 비트 오차율 식의 수치적 결과와 시뮬레이션 결과를 비교하여 유도된 식을 검증하고, 중계노드의 수에 따른 비트 오차율 성능 변화를 관찰한다.

• Journal of Communications and Networks
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• 제8권1호
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• pp.1-7
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• 2006

Quadrature amplitude modulation-spread spectrum (QAM-SS) and code division multiplexing (CDM) are multi-level modulation schemes with high performance but they cause a large peak-average power ratio (PAPR). Therefore, this paper proposes a novel modulation scheme for high-rate transmission which follows a sequence of CDM-mapping-CDM not only to correct the above-mentioned problem but also offer a high flexibility in obtaining arbitrary multilevel modulation with very low implementation complexity and high performance.

• Current Optics and Photonics
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• 제2권6호
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• pp.532-539
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• 2018

Multiple LED arrays can be utilized in visible-light communication (VLC) to improve communication efficiency, while maintaining smart illumination functionality through dimming control. This paper proposes a modulation scheme called "Spatial Intensity Modulation" (SIM), where the effective number of turned-on LEDs is employed for data modulation and dimming control in VLC systems. Unlike the conventional pulse-amplitude modulation (PAM), symbol intensity levels are not determined by the amplitude levels of a VLC signal from each LED, but by counting the number of turned-on LEDs, illuminating with a single amplitude level. Because the intensity of a SIM symbol and the target dimming level are determined solely in the spatial domain, the problems of conventional PAM-based VLC and related MIMO VLC schemes, such as unstable dimming control, non uniform illumination functionality, and burdens of channel prediction, can be solved. By varying the number and formation of turned-on LEDs around the target dimming level in time, the proposed SIM scheme guarantees homogeneous illumination over a target area. An analysis of the dimming capacity, which is the achievable communication rate under the target dimming level in VLC, is provided by deriving the turn-on probability to maximize the entropy of the SIM-based VLC system. In addition, a practical design of dimmable SIM scheme applying the multilevel inverse source coding (MISC) method is proposed. The simulation results under a range of parameters provide baseline data to verify the performance of the proposed dimmable SIM scheme and applications in real systems.

• Wind and Structures
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• 제18권6호
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• pp.693-715
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• 2014

Stochastic processes are used to represent phenomena in many diverse fields. Numerical simulation method is widely applied for the solution to stochastic problems of complex structures when alternative analytical methods are not applicable. In some practical applications the stochastic processes show non-Gaussian properties. When the stochastic processes deviate significantly from Gaussian, techniques for their accurate simulation must be available. The various existing simulation methods of non-Gaussian stochastic processes generally can only simulate super-Gaussian stochastic processes with the high-peak characteristics. And these methodologies are usually complicated and time consuming, not sufficiently intuitive. By revealing the inherent coupling effect of the phase and amplitude part of discrete Fourier representation of random time series on the non-Gaussian features (such as skewness and kurtosis) through theoretical analysis and simulation experiments, this paper presents a novel approach for the simulation of non-Gaussian stochastic processes with the prescribed amplitude probability density function (PDF) and power spectral density (PSD) by amplitude modulation and phase reconstruction. As compared to previous spectral representation method using phase modulation to obtain a non-Gaussian amplitude distribution, this non-Gaussian phase reconstruction strategy is more straightforward and efficient, capable of simulating both super-Gaussian and sub-Gaussian stochastic processes. Another attractive feature of the method is that the whole process can be implemented efficiently using the Fast Fourier Transform. Cases studies demonstrate the efficiency and accuracy of the proposed algorithm.

• Current Optics and Photonics
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• 제6권1호
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• pp.39-43
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• 2022

Underwater optical wireless communication (UOWC) is a good candidate for high-speed underwater wireless communication. In this work, we compare the performance of several modulation techniques for a UOWC system consisting of a light-emitting diode (LED) with an operating wavelength of 405 nm and a Si avalanche photodiode (APD). In this work, we consider six modulation schemes: 4-quadrature amplitude modulation (QAM), 8-QAM, quadrature phase shift keying (QPSK), binary phase shift keying (BPSK), on-off keying (OOK), and 4-pulse amplitude modulation (PAM). We also consider the cases of pure water and seawater for the working conditions. Our results show that 4-QAM and 8-QAM perform the best, in terms of communication distance and transmission power efficiency, for all water types considered.

• Journal of Power Electronics
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• 제16권4호
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• pp.1407-1414
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• 2016

Unlike existing pulse-width modulation (PWM) techniques, such as sinusoidal PWM and random PWM, the wavelet PWM (WPWM) technique based on a Harr wavelet function can achieve a high fundamental component for the output voltage, low total harmonic distortion, and simple digital implementation. However, the original WPWM method lacks output voltage control. Thus, the practical application of the WPWM technique is limited. This study proposes an improved WPWM technique that can regulate output voltage amplitude with the addition of a parameter. The relationship between the additional parameter and the output voltage amplitude is analyzed in detail. Experimental results verify that the improved WPWM exhibits output voltage control in addition to all the merits of the WPWM technique.