• Title/Summary/Keyword: HPA

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Predistortion Technique for Linearizing High Power Amplifier (고출력 증폭기의 비선형성 보상을 위한 사전왜곡 기술에 관한 고찰)

  • Kim, S.;Jin, M.;Oh, D.G.
    • Electronics and Telecommunications Trends
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    • v.18 no.2 s.80
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    • pp.53-66
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    • 2003
  • 고출력 증폭기(HPA)는 위성통신 등 무선통신 시스템의 송신단에서 필수적으로 요구되는 요소 중의 하나이다. 그러나, 대부분의 HPA들은 비선형적인 출력 특성을 가지고 있으므로 이로 인한 신호의 왜곡으로 전송 손실을 야기하게 된다. 이러한 문제점을 해결하기 위하여 HPA를 선형화하는 가장 효율적인 방법으로 제안되어온 것이 사전왜곡(predistortion) 기법이다. 본 고에서는 고출력 증폭기의 비선형성을 보상하기 위한 사전왜곡 방식의 기본 개념과 다양한 사전왜곡 방식에는 어떤한 것들이 있는지 그 기본 원리 및 기술 개발 동향에 관하여 고찰한다.

Effects of Lycii Radicis Cortex in HPA-Axis System on the Forced Swimming Test (지골피(地骨皮)가 강제수영부하실험에서 HPA-Axis System에 미치는 영향)

  • Koo, Beom-Mo;Lee, Tae-Hee
    • Herbal Formula Science
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    • v.18 no.2
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    • pp.215-225
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    • 2010
  • In order to investigate the antidepressant effects of Lycii Radicis Cortex on the change of HPA-Axis system, the forced swimming test was performed. The expressions of CRF and c-Fos in the PVN were measured with immunohistochemical method and the concentration of ACTH in Serum was evaluated with ELISA method. And the results obtained were as follows. Results : 1. The duration of immobility in the forced swimming test was significantly decreased in the LRC100 group and the LRC400 group(P<0.001). 2. The expressions of CRF and c-Fos were significantly reduced in the LRC100 group and the LRC400 group(P<0.001). And the concentration of ACTH in Serum were significantly reduced in the LRC 100 group(P<0.05). According to the results above mentioned, it can be considered that Lycii Radicis Cortex has antidepressant effects.

Performance improvement of the high speed mobile communication by the predistorter (전치왜곡기로 인한 고속이동통신의 성능향상기법)

  • Lee, Kang-Mi;Shin, Duck-Ho;Kim, Bak-Hyun;Lee, Jun-Ho
    • Proceedings of the IEEK Conference
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    • 2006.06a
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    • pp.173-174
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    • 2006
  • High power amplifier (HPA), which is used in transmitter of wireless communication systems, usually works in near saturation point in order to achieve maximum efficiency. In this region, HPA can introduce undesirable nonlinear effects. In this paper, we present a polynomial modeling method for efficient techniques to compensate for nonlinear distortion introduced by nonlinear HPA. Proposed polynomial predistorter inverses actual amplifier. Namely, we derive polynomials of amplifiers from analytical method and the electrical parameters in the data sheet of an actual amplifier and then can derive polynomial predistorter by inversing them. It is an effective and a simple method to compensate nonlinear distortion. SSPA(Solid-state power amplifier) is considered. We also analyze the effects of predistortion on the SER performance of communication system with 16-QAM modulation format. The results have shown the efficiency of this model.

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On Compensating Nonlinear Distortions of an OFDM System Using an Efficient Adaptive Predistorter (효과적인 적응 전처리왜곡기를 이용한 OFDM 시스템에서의 비선형 왜곡 보상)

  • 강현우;조용수;윤대희
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.4
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    • pp.696-705
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    • 1997
  • This paper presents an efficient adaptive predistortion technique compensating linear and nonlinear distortions caused by high-power amplifier (HPA) with memory in OFDM systems. The efficient adaptive data predistortion techniques proposed for compensation of HPA with memory in single carrier systems cannot be applied to OFDM systems since the possible input levels for HPA is infinite in OFDM systems. Also, previous adaptive predistortion techniques, based on Volterra series modeling, are not suitable for real-time implementation due to high computational burden and slow convergence rate. In the proposed approach, the memoryless HPA preceded by a linear filter in OFDM systems is modeled by the Wiener system which is then precompensated by the proposed adaptive predistorter with a minimum number of filter taps. An adaptive algorithm for adjusting the proposed adaptive predistorter is derived using the stochastic gradient method. It is demonstrated by computer simulation that the performance of OFDM system suffering from nonlinear distortion can be greatly improved by the proposed efficient adaptive predistorter using a small number of filter taps.

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Determination of Cadmium, Chromium and Lead in Polymers by ICP-OES Using a High Pressure Asher (HPA)

  • Cho, Hong-Je;Myung, Seung-Woon
    • Bulletin of the Korean Chemical Society
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    • v.32 no.2
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    • pp.489-497
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    • 2011
  • The proposed method for an effective assay of Cd, Cr and Pb in several polymer samples has been validated. The determination was carried out using ICP-OES after a high pressure asher (HPA) digestion at pressure and temperatures up to 13 MPa and $320^{\circ}C$, respectively. Polymer based materials were totally oxidized with nitric acid in a HPA chamber and determined by ICP-OES. Validation parameters such as linearity, matrix effect, limit of dectection (LOD), limit of quantitation (LOQ), accuracy and precision (repeatibility, intermediate precision and reproducibility) were assessed. The LOD and LOQ in the sample were ranged from 0.98 to 1.18 mg $kg^{-1}$ and 2.93 to 3.55 mg $kg^{-1}$, respectively, relying on the analyte. The proposed method had a good accuracy and precision for repeatability, intermediate precision with respect to days and analysts and reproducibility expressed as inter-laboratory study. The developed method was simple to use, suitable and applicable to various kinds of polymers.

Design and Implementation of High Power Amplifier for PCS Pico Cell (PCS Pico Cell용 전력증폭기의 설계 및 제작)

  • 김선영;방성일
    • Proceedings of the IEEK Conference
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    • 2001.06a
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    • pp.189-192
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    • 2001
  • In this paper, We designed and implemented 20 watt high power amplifier which can be used for the commercial services in band of 1.86 ~ 1.870Hz at PCS. In order to satisfy ACPR, We designed by using the ADS(Advanced Design System)ver1.3. The HPA is fabricated on tepron substrate($\varepsilon_{{\gamma}}$ =3.15, H=0.78mm, T=0.02mm). The implemented HPA measured The ACPR characteristics at $\pm$ 885kHz, $\pm$ 1.25MHz, $\pm$2.25MHz. The HPA meets specification with good ACPR. The HPA is expected to use as a commercial product of PCS base station.roduct of PCS base station.

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Analysis of Phase Noise and HPA Non-linearity in the OFDM/FH Communication System (OFDM/FH 시스템에서 위상잡음과 비선형 HPA의 특성분석)

  • Li, Ying-Shan
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.649-659
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    • 2003
  • OFDM/FH communication system Is widely used in the wireless communication for the large capacity and high-speed data transmission. However, phase noise and PAPR (peak-to-average power ratio) are the serious problems causing performance impairment. In this paper, PLL (phase locked loop) frequency synthesizer with high switching speed is used for the phase noise model. SSPA and TWTA are considered for the nonlinear HPA model. Under these conditions and by approximating $e^{j{\phi}[m]}$ into $1 + j{\phi}[m]-\frac{1}{2}{\phi}^2[m]$ for the phase noise nonlinear approximation, SINR (signal-to-interference-noise-ratio) with nonlinear HPA and phase noise is derived in the OFDM/FH system. The bit error probabilities (BER) are found by computer simulation method and semi-analytical method. The simulation results closely match with the semi-analytical results.

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Decision making for CDMA HPA Bias used Fuzzy Logic Controller (퍼지제어기를 이용한 CDMA중계기의 최적동작점 결정)

  • 김성식;홍광진;조현찬;오창헌;김두용;이규영
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 2003.05a
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    • pp.283-286
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    • 2003
  • Generally, the repeater in CDMA(Code Division Multiple Access) included HPA(HI-Power Amplifier) to amplifier communication signals. Also, HPA contained PD(Predistortor) to maintain the linearization of amplifier characteristics A configuration component of PD have been used electricity nonlinear devices such that diode. But this diode takes many influences at the circumstance temperature. Consequently, st can't maintain output linearization, and drop the communication Duality. The manufacturer set bias of the circuit to the manual at the first out of ware-house low. But the Q-point changes according to the change of the high temperature or low temperature. Therefore, we designed a system to maintain the Q-point by FDM(Fuzzy Decision Maker) in this paper.

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Analysis of Nonlinear Distortions OFDM Systems (OFDM 시스템의 비선형 왜곡 분석)

  • 전원기;조용수
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 1998.06a
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    • pp.165-170
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    • 1998
  • In this paper, the effect of nonlinear distortion, caused by a high-power amplifier (HPA) in an orthogonal frequency division multiplexing (OFDM) system, on the receiver part is analyzed. Since the HPA, which can be modeled by a memoryless Volterra system, distorts OFDM signals in a nonlinear fashion, the received signal at each subchannel includes the multiplicative distortion of 1-st order as well as additive nonlinear distortion of higher-order. The nonlinear distortion can be viewed as a nonlinear interchannel interference (NICI) since it consists of harmonic distortions and intermodulation distortions, produced by other subchannels affecting the subchannel of interest. In this paper, were analytically derive the variance of NICI in terms of average input power using the Volterra model for HPA, and then calculate the bit-error rate (BER) performance of an OFDM system. Also, we propose a simple method to compensate for the phase distortion in OFDM system amplified by HPA, and calculate its BER performance. Validity of the proposed approach is verified by computer simulations for an OFDM system employing 16-QAM constellation input.

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Review on the Human Powered Aircraft Development (인간동력 항공기 개발 고찰)

  • Han, Cheolheui
    • Journal of Institute of Convergence Technology
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    • v.4 no.2
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    • pp.35-40
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    • 2014
  • Human powered aircraft (HPA) is an airplane that uses only human power for its propulsion. It's development is completely different from conventional aircraft that use fuels as a power source. In the present study, special features for the development of HPA are discussed by studying the design requirements, weight estimation, aerodynamics and propulsion studies, power analysis, and mossion profile design. It is found that the development of the HPA is completely different from conventional aircraft. Mission profile is crucial to the successful flight of the sport HPA when the pilots are changed.