• MALSORI
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• no.64
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• pp.89-103
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• 2007

In this paper, we introduce mel-cepstrum modulation energy (MCME) for a feature to discriminate speech and music data. MCME is a mel-cepstrum domain extension of modulation energy (ME). MCME is extracted on the time trajectory of Mel-frequency cepstral coefficients, while ME is based on the spectrum. As cepstral coefficients are mutually uncorrelated, we expect the MCME to perform better than the ME. To find out the best modulation frequency for MCME, we perform experiments with 4 Hz to 20 Hz modulation frequency. To show effectiveness of the proposed feature, MCME, we compare the discrimination accuracy with the results obtained from the ME and the cepstral flux.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.12
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• pp.1086-1093
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• 2013

In this paper, we propose a novel modulation that combines the spatial modulation (SM) with the subcarrier intensity-modulation (SIM) for optical wireless communications. The performance of SIM-SM scheme is compared to a conventional SIM by computer simulation. For the spectral efficiency (SE) of 2bits/s/Hz, the performance gain about 2dB is achieved. As the SE increases to 3bit or 4bits/s/Hz, the Eb/N0 gain becomes about 5dB. It is shown the attenuation for the SIM is more serious than the SIM-SM according to increasing the number of the subcarriers.

• Journal of Power Electronics
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• v.10 no.3
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• pp.277-284
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• 2010

This paper presents a novel hybrid carrier based space vector modulation for cascaded multilevel inverters. The proposed technique inherits the properties of carrier based space vector modulation and the fundamental frequency modulation strategy. The main characteristic of this modulation are the reduction of power loss, and improved harmonic performance. The carrier based space vector modulation algorithm is implemented with a TMS320F2407 digital signal processor. A Xilinx Complex Programmable Logic Device is used to develop the hybrid PWM control algorithm and it is integrated with a digital signal processor for hybrid carrier based space vector PWM generation. The inverter offers less weighted total harmonic distortion and it operates with equal electrostatic and electromagnetic stress among the power devices. The feasibility of the proposed technique is verified by spectral analysis, simulation, and experimental results.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.670-674
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• 2016

The control performance of hybrid PWM inverter using a phase current measurement is presented in this paper. The hybrid PWM technique consists of space vector pulse width modulation (SVPWM) and six-step voltage control operation. The SVPWM is performed to reduce the harmonic components in the low speed region, and the six-step modulation is applied to increase the maximum speed of the IPMSM in the high speed region. Therefore, it is possible to obtain a great performance in both the low speed range and high speed range. However, the six-step modulation cannot be completely implemented, since the inverter that includes the lag-shunt sensing method has an immeasurable current region. In this paper, a quasi-six-step modulation using a modified voltage vector is proposed. The validity and usefulness of the proposed PWM technique is verified by MATLAB/Simulink and experimental results.

• 한국신재생에너지학회:학술대회논문집
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• 2009.11a
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• pp.491-491
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• 2009

Wind turbines produce aerodynamic noise which fluctuate periodically at a blade passing frequency. This sound characteristic is called amplitude modulation, or swishing sound. Several previous studies claimed that this amplitude modulation has a possibility to increase noise annoyance. Thus, this study performed a listening test to find the relationship between the amplitude modulation in wind turbine noise on noise annoyance. The stimuli for the listening test was recorded from a 1.5MW wind turbine in Jeju island. The result of the listening test shows that the amplitude modulation in wind turbine noise significantly increase noise annoyance. Moreover, this study analytically examined the effect of amplitude modulation on noise perception. The result indicates that amplitude modulated sound can be easily perceived even though the background noise level is higher than the sound level of the signal.

• ETRI Journal
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• v.35 no.2
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• pp.188-192
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• 2013

Previous work proposed combining multipulse pulse position modulation (MPPM) with pulse amplitude modulation to form multipulse amplitude and position modulation (MPAPM), which is a hybrid modulation that results in an improvement in bandwidth efficiency but a degradation in power efficiency. In this paper, to achieve greater power efficiency and a better data rate, we propose multipulse dual amplitude-width modulation, based on MPAPM and pulse width modulation. The proposed scheme shows a remarkable improvement in data rate and a 1.5-dB improvement in power efficiency over MPAPM, while sustaining the bandwidth efficiency. After introducing symbol structure, we present the theoretical expressions of spectral efficiency, the power requirements, and the normalized data rate, as well as the results of comparing the proposed modulation to MPPM and MPAPM.

• Journal of the Optical Society of Korea
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• v.12 no.4
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• pp.303-308
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• 2008

Directly modulated fiber-optic links generally suffer higher link loss and larger signal distortion than externally modulated links. These result from the electron-photon conversion loss and laser modulation dynamics. As a method to overcome the drawbacks, we have experimentally demonstrated the RF performance of directly modulated, ultra-strong injection-locked gain-lever distributed Bragg reflector (DBR) lasers. The free-running DBR lasers exhibit an improved amplitude modulation efficiency of 12.4 dB under gain-lever modulation at the expense of linearity. By combining gain-lever modulation with ultra-strong optical injection locking, we can gain the benefits of both improved modulation efficiency from the gain-lever effect, plus improved linearity from injection locking. Using an injection ratio of R=11 dB, a 23.4-dB improvement in amplitude response and an 18-dB improvement in spurious-free dynamic range have been achieved.

• International journal of advanced smart convergence
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• v.8 no.3
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• pp.61-68
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• 2019

Spatial modulation (SM) is the first proposed space modulation technique. By further utilizing the quadrature spatial dimension, quadrature spatial modulation (QSM) has been developed as an amendment to SM system to enhance the overall spectral efficiency. Both techniques are capable of entirely eliminating interchannel interference (ICI) at the receiver. In this paper, we propose a simple adaptive hybrid switching transmission scheme to obtain better system performance than SM and QSM systems under a fixed transmission date rate. The presented modulator selection criterion for switching between spatial modulator and quadrature spatial modulator is based on the larger received minimum distance of spatial modulator and quadrature spatial modulator to exploit the spatial channel freedom. It is shown through Monte Carlo simulations that the proposed hybrid SM and QSM switching system yields lower error performance than the conventional SM and QSM systems under the same fixed data rate and thus can provide signal to noise ratio (SNR) gain.

• Journal of Power Electronics
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• v.19 no.1
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• pp.99-107
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• 2019

This study proposes a new modulation strategy to deal with unbalanced output voltage that is based on three-level neutral-point-clamped cascaded rectifiers. The fundament idea is to reallocate the value of the voltage levels generated by each of the modules on the basis of space vector pulse width modulation. This proposed modulation strategy can reduce the switching frequency while maintaining the mutual-module voltage balance. First, an analysis of unbalanced output voltage is reflected. Then a new modulation strategy is introduced in detail. Internal module capacitor voltages are balanced by the selection of redundant vectors. Moreover, the voltage balance ability is calculated. Finally, the feasibility of this modulation strategy is verified through experimental results.

• ETRI Journal
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• v.38 no.4
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• pp.606-611
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• 2016

This paper presents antenna selection schemes for recently proposed quadrature spatial modulation (QSM) systems. The antenna selection strategy is based on Euclidean distance optimized antenna selection (EDAS). The symbol error rate (SER) performance of these schemes is compared with that of the corresponding algorithm associated with spatial modulation (SM) systems. It is shown through simulations that QSM systems using EDAS offer significant improvement in terms of SER performance over SM systems with EDAS. Their SER performance gains are seen to be about 2 dB-4 dB in $E_s/N_0$ values.