• Journal of the Korea Computer Industry Society
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• v.6 no.3
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• pp.429-436
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• 2005

The linear modulation method which has high spectrum efficiency when applying in mobile communication system, the problem occurs. In order to solve like this problem non-linearity characteristic of the power amplifier linearity against the method which it does it investigated. It used a design objection and it implemented the microwave power amplifier. The amplifier which it produces used the micro-strip line and when it imput power 13 dBm from center frequency, the possibility of getting the output power of 28 dBm.

• Journal of Advanced Navigation Technology
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• v.2 no.2
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• pp.116-125
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• 1998

Most of modern mobile communication systems require low distortion in addition to high power and high efficiency characteristics for power amplifiers. The power amplifiers cause adjacent channel interference by intermodulation and spectral regrowth. In order to analyze the effects of the power amplifier on communication system, a 22Mcps spreaded digital modulated signal source and a ISM band power amplifier have been constructed, ACPR characteristics are simulated and measured for the RZ and NRZ encoded signals.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.2
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• pp.194-204
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• 2002

In this paper, a new two-phase space vector RPWM(Random PWM) is proposed. In the proposed RPWM, each of two-phase PWM pulses is located randomly in each switching interval. Based on the space vector modulation technique, the duty ratio of the pulses is calculated. Along with the randomization of the PWM pulses, we can obtain the effects of spread spectra of inverter output voltage, d.c link current and audible switching acoustic noise as in the case of randomly changed switching frequency. To verily the validity of the proposed two-phase RPWM scheme, the experiment based on the Cl67 micro-controller was executed. The performance of the proposed scheme was compared with traditional PWM schemes experimentally.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.92-97
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• 2007

Switching mode amplifiers have been studied widely for use at microwave frequency range, and the class E amplifier which is a type of switching mode amplifier offers very high efficiency approaching 100%. In this paper, 2.4GHz microwave class E amplifier with 66% power added efficiency (PAE) and 17.6dBm output has been linearized for use at wireless LAN transmitter, and digital predistortion technique with look up table is applied. With -3dBm input power of wireless LAN, measured output spectrum can meet the required IEEE 802.11g standard spectrum mask, and the digital predistortion output spectrum has been improved by 5dB of ACPR at 20MHz offset from center frequency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.4
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• pp.145-150
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• 2010

In this paper, we propose additional data transmission system for spectrum efficiency improvement and derive channel capacity formula as a approximated closed-form. Spread spectrum watermarking scheme is selected for the watermarking embedder. Nakagami-q (Hoyt) model is considered as a multipath fading channel. Numerical results show the channel capacity variation of the proposed system in wireless fading channel. From the results, we confirm that the channel capacity of the watermarking system is affected by the fading coefficient and system parameters such that host sampling frequency, host-to-watermark ratio, watermark-to-noise ratio, and PN sequence length.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.364-371
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• 2004

This thesis is proposing novel RPWM(Random PWM) techniques that can locate PWM pulse to do random. RPWM techniques to propose locates SVPWM(Space Vector PWM) pulse by number of each random and principle to locate of pulse applies different random function and locate pulse. For propriety verification of proposed techniques, achieve an simulation and experiment that use MATLAB/SIMULINK about proposed RPWM techniques algorithm and IGBT inverter composition that use DSP(TMS320C31). Specially, analyze harmonic spectra of inverter output current when the induction motor speed is more than 10,000 rpm, confirm that RPWM's effect in high speed degree appears. Proposed RPWM techniques propriety prove from reduction effect of harmonic magnitude that corresponds to an integer times of switching frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.64-73
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• 2000

Since so many potentials of services, applications, marketing and regulation, it is difficult to decide the fair pricing scheme of network services. However, these considerations are not particular to the operation of a communications network, which is closely related to technological constraints for QoS guarantee. In this paper, the power spectral analysis of MPEG video based on the P-MMBBP model is discussed in the manner of the QoS degradation to the packet delay. As a consequence of the QoS-degradation, a new fair-pricing scheme with the discount factor is proposed. As a result, the proposed scheme shows good characteristics to guarantee the fairness of the charging in the Internet wide-area network.

• Journal of IKEEE
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• v.21 no.1
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• pp.89-91
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• 2017

We proposed a spatial modulation (SM) scheme to improve spectral efficiency of multi-input multi output (MIMO) systems by using double multi-strata space-time codes (D-MSSTC). For improving the performance of proposed scheme, we allocate transmit power and phase to layers in each MSSTC, and assign rotation angle to SM codebooks. Additionally, we jointly optimize power, phase and rotation angle to maximize the minimum coding gain distance of D-MSSTC-SM. It is observed that the proposed scheme shows better error performance with high spectral efficiency than conventional schemes in simulation results.

• Applied Chemistry for Engineering
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• v.19 no.3
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• pp.322-325
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• 2008

3,3-Dimethyl-1-butene ($C_6H_{12}$) monomer was deposited using a plasma-enhanced chemical vapor deposition (PECVD) instrument. The more the R.F. power/pressure ratio in FT-IR spectrum, the less the hydrogen quantity and the dangling bond in amorphous carbon films observed so that the mechanical property of the films are improved related to the density. Also, with the increase D peak in Raman spectrum is increased and the ring structure's films are produced. According to these results, hardness and modulus are 12 GPa and 85 GPa, respectively. The refractive index (n) and extinction coefficients (k) of the deposited films are increased with the increase in a power/pressure ratio.

• Journal of radiological science and technology
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• v.44 no.1
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• pp.31-37
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• 2021

This study aim of quantitative assessment of Noise Power Spectrum(NPS) and image characteristics of by acquired the optimal image for noise characteristics and quality assurance by using magnetic resonance imaging(MRI). MRI device was (MAGNETOM Vida 3.0T MRI; Siemense healthcare system; Germany) used and the head/neck shim MR receive coil were 20 channels coil and a diameter 200 mm hemisphere phantom. Frequency signal could be acquired the K-space trajectory image and white image for NPS. The T2 image highest quantitatively value for NPS finding of showed the best value of 0.026 based on the T2 frequency of 1.0 mm-1. The NPS acquired of showed that the T1 CE turbo image was 0.077, the T1 CE Conca2 turbo image was 0.056, T1 turbo image was 0.061, and the T1 Conca2 turbo image was 0.066. The assessment of NPS image characteristics of this study were to that could be used efficiently of the MRI and to present the quantitative evaluation methods and image noise characteristics of 3.0T MRI.