• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1262-1270
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• 2007

In this paper, we propose a new distortion cancellation mechanism for a balanced power amplifier structure using the carrier cancellation loop of a feedforward and post-distortion technique. The proposed cross post-distortion balanced linear amplifier can reduce nonlinear components as much as the conventional feedforward amplifier through the output dynamic range and broad bandwidth. Also the proposed system provides higher efficiency than the feedforward. The capacities of power amplifier and error power amplifier in the proposed system are analyzed and compared with those of feedforward amplifier. Also the operation mechanisms of the three kind loops are explained. The proposed cross post-distortion balanced linear power amplifier is implemented at the IMT-2000($f_0=2.14\;GHz$) band. With the commercial high power amplifiers of total power of 240 W peak envelope power fer base-station application, the adjacent channel leakage ratio measurement with wideband code division multiple access 4FA signal shows 18.6 dB improvement at an average output power of 40 dBm. The efficiency of fabricated amplifier Improves about 2 % than the conventional feedforward amplifier.

• Journal of Electrical Engineering and Technology
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• v.13 no.6
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• pp.2441-2446
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• 2018

This paper presents a radio frequency-to-direct current (RF-to-DC) converter for special RF power harvesting application at 915 MHz. The major featured components of the proposed RF-to-DC converter is the combination of a cross-coupled rectifier and an active diode: first, the cross-coupled rectifier boosts the input voltage to desired level, and an active diode blocks the reverse current, respectively. A prototype was implemented using $0.18{\mu}m$ CMOS technology, and the performance was proven from the fact that the targeted RF harvesting system's full-operation with higher power efficiency; even if the system's input power gets lower (e.g., from nominal 0 to min. -12 dBm), the proposed RF-to-DC converter constantly provides 1.47 V, which is exactly the voltage level to drive follow up system components like DC-to-DC converter and so on. And, maximum power conversion efficiency is 82 % calculated from the 0 dBm input power, 2.3 mA load current.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.4
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• pp.215-224
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• 2009

Analysis for various driven nozzle position changes. The analysis was done for different Reynolds number in entrance region of jet-pump and for several diameter ratios of driven nozzle. (1) The largest absorption energy was found at the point s=1 in condition of diameter ratio 1:3.21 and point s=0.5 in condition of diameter ratio 1:2.25. (2) The absorption energy was not related to the change of entrance velocity and the driven nozzle position having the largest absorption energy was function for cross section ratio. (3) As the position of driven nozzle moves to the downstream, the absorption energy gets weaker. Because the energy from swirl was lost at the cross section gets smaller. (4) As the position of driven nozzle moves to the downstream, the injection energy leans to the upper direction wall and as the Reynolds number increase, the lean phenomenon is more distinct. (5) The flow quantity of driven nozzle, the diameter ratio 1:3.21, was 32% higher than that of 1 : 2.25 and as the inlet velocity gets faster the efficiency decreased. And as the cross section of the driven nozzle increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3A
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• pp.248-256
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• 2004

Woerner had suggested an asynchronous trellis-coded DS/CDMA system based on a multi-sequence signaling, biorthogonal sequence, which is superior to single sequence signaling, such as M-ary PSK, due to their better cross-correlation properties. This paper analyzes and compares system performance between OPSM, a recently-presented multi-sequence signaling scheme, and biorthogonal sequence signaling. Interuser interference moments of the two schemes are derived and compared which verifies that OPSM, having smaller signature sequences per symbol than biorthogonal signaling, reduces cross-correlation. Numerical results compare the power and spectral efficiency of asynchronous trellis-coded DS/CDMA systems based on multi-sequence signaling.

• Tribology and Lubricants
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• v.31 no.6
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• pp.239-244
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• 2015

Chemical mechanical polishing (CMP) is one of the most important processes for enabling sub-14 nm semiconductor manufacturing. Moreover, post-CMP defect control is a key process parameter for the purpose of yield enhancement and device reliability. Due to the complexity of device with sub-14 nm node structure, CMP-induced defects need to be fixed in the CMP in-situ cleaning module instead of during post ex-situ wet cleaning. Therefore, post-CMP in-situ cleaning optimization and cleaning efficiency improvement play a pivotal role in post-CMP defect control. CMP in-situ cleaning module normally consists of megasonic and brush scrubber processes. And there has been an increasing effort for the optimization of cleaning chemistry and brush scrubber cleaning in the CMP cleaning module. Although there have been many studies conducted on improving particle removal efficiency by brush cleaning, these studies do not consider the effects of brush contamination. Depending on the process condition and brush condition, brush cross contamination effects significantly influence post-CMP cleaning defects. This study investigates brush cross contamination effects in the CMP in-situ cleaning module by conducting experiments using 300mm tetraethyl orthosilicate (TEOS) blanket wafers. This study also explores brush pre-treatment in the CMP tool and proposes recipe effects, and critical process parameters for optimized CMP in-situ cleaning process through experimental results.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.2
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• pp.74-79
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• 2008

The fracture strength of cross groove type constant velocity joint is largely determined by the fracture strength of the cage having window-like pockets for retaining the torque transmitting balls. A stress distribution acting on the cage is influenced by rigidities of the rim portion and of the column members, therefore requires a calculation such as FEA. To analyze fracture strength of cage, a 3-D elasto-plastic finite element analysis and a submodeling technique are used to achieve both computational efficiency and accuracy. The results are in reasonably good agreement with experiment.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.17 no.2
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• pp.131-139
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• 1988

The thermoacoustic oscillation induced in an air column with variable cross section area is investigated theoretically and experimentally. The onset condition of the oscillation is derived by equating the acoustic power production to the power dissipation. The power production at the heater is predicted by using the efficiency factor obtained by heat transfer analysis for a single wire in a uniform cross flow and considering the interference between heater wires. The power dissipation is estimated by measuring the attenuating coefficient from the pressure decay curve. The theoretical prediction to the onset condition of the oscillation is confirmed experimentally. The effect of the variation of the column cross section area on the onset condition is presented.

• Special Issue of the Society of Naval Architects of Korea
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• 2008.09a
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• pp.29-32
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• 2008

Hinged cross bar which is fitted for buyer's special item in cell guide of container vessels has an advantage of efficiency on container loading. In this paper, the main focus is to confirm the structural adequacy of hinged cross bar supporting structure in cell guide under the considered loading condition for container vessel.

• The Korean Journal of Applied Statistics
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• v.14 no.1
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• pp.59-70
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• 2001

이면교배 실험은 식물이나 동물의 교배를 통해 자식계통의 유전적인 성질을 조사하는데 중용한 역할을 한다. 이면교배에 관한 기존의 연구에서는 p개의 자식계통은 하나의 집합에 속하는 것으로 간주하였다. 이와 달리 새로 육성된 자식계통의 유전적 성질을 평가하고자 하는 경우에는, p개의 자식계통이 각각 p$_1$과 p$_2$개의 자식계통을 갖는 두 개의 집합으로 분리되는 형태의 교배실험을 사용한다(단, p=p$_1$+p$_2$). 이에 본 연구에서는 자식계통이 두 집단으로 분리된 경우에 대해서 Kempthorne의 합동식을 이용하여 두 군간 교배에 대한 블록디자인을 설계하고, 이에 대한 평균효율인자를 계산하는 방법을 제안하고자 한다.

• Proceedings of the KIEE Conference
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• 2004.10a
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• pp.185-187
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• 2004

In many multiple output SMPS, the cross regulation between the output voltage is so poor that the linear regulator is usually added to avoid this problem. Therefore, manufacturing cost is increased. In this paper, the TTFC(Two Transistor Forward Converter) using the magamp was presented to obtain better cross regulation between the multiple output SMPS. Also, as the synchronous rectifier was applied in the secondary section, whole efficiency can be improved. In this paper, the mode analyses in steady slate and experimental results of the prototype to verify the validity of the presented converter are presented and discussed.