• Title/Summary/Keyword: HPA

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The Design and Construction Consideration for Developing the Human Powered Aircraft (인력비행기 개발을 위한 설계 및 제작 고려 요소)

  • Lee, Ki-Young;Choi, Seong-Ok
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.17 no.1
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    • pp.29-38
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    • 2009
  • This paper surveys the historical perspective and design considerations for developing the human powered aircraft(HPA). Especially the weight and materials, aerodynamics, flight controls, and power trains are focused. The average power a human can produce and sustain is approximately 200${\sim}$250 W which is a critical design constraint of HPA. The survey shows that the empty weight of HPA was in the 30${\sim}$40 kg range(90${\sim}$110 kg include pilot). Thus, in order to design a successful HPA, the value of power to weight ratio should be 2.0 W/kg or above. The HPA design technique could be applied directly to the development of an unmanned high altitude airplanes used for atmospheric research, where light structures, low Reynolds number aerodynamics and high efficiency propeller design are required as well.

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Study on an Enhanced Adaptive Pre-distorter Linearizing Nonlinear Distortions of a High Power Amplifier (고출력 증폭기의 비선형 왜곡을 선형화하는 향상된 적응 사전 왜곡기에 대한 연구)

  • Kwon, Oh Sang
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.10 no.4
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    • pp.143-150
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    • 2014
  • A high power amplifier(HPA) has widely been used in wireless communications. In order to have a maximum power efficiency, the HPA uses a saturation domain having nonlinear characteristics, which generates nonlinear distortions to decrease the transmission efficiency. In order to solve this problem, various methods to linearize HPA have been reported until now, and the pre-distorter method is very attractive among them. In this paper, a new enhanced adaptive pre-distorter method was proposed to be applied for compensating nonlinear distortions of HPA. Through computer simulations as well as the analytical analysis, it could be shown that it is possible for both conventional adaptive pre-distorter and proposed adaptive pre-distorter, to be applied for linearizing HPA. Also, the simulations results demonstrated that the proposed adaptive pre-distorter may have faster convergence speed and better capability of compensating the nonlinear distortion than the conventional adaptive pre-distorter with nearly equal computation complexity.

THE RELATION BETWEEN HPA AND COMS MULTI-CARRIER

  • Park Durk-Jong;Yang Hyung-Mo;Hyun Dae-Wan;Ahn Sang-Il;Kim Eun-Kyu
    • Proceedings of the KSRS Conference
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    • 2005.10a
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    • pp.564-566
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    • 2005
  • The relation between HPA (High Power Amplifier) and COMS (Communication Ocean Meteorological Satellite) multi-carrier is analyzed in this paper. MODAC (Meteorological and Ocean Data Application Center) has a primary mission to transmit processed data, HRIT (High Rate Information Transmission) and LRIT (Low Rate Information Transmission), which is normalized and calibrated by pre-processing. It is also replaced with the SOC (Satellite Operation Center) in emergency case and can transmit the command and ranging tones for operation of COMS. From the result of simulation with modelled HPA, it is found that the multi-carrier in one HPA can give rise to an inter-modulation which makes harmonic and spurious elements increase in-band. Under the environment of these increased parasitic elements, the degradation of multi-carrier's quality is estimated from the ratio of the amount of noise to total output power of HPA.

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Parallel M-band DWT-LMS Algorithm to Improve Convergence Speed of Nonlinear Volterra Equalizer in MQAM System with Nonlinear HPA (비선형 HPA를 가진 M-QAM 시스템에서 비선형 Volterra 등화기의 수렴 속도 향상을 위한 병렬 M-band DWT-LMS 알고리즘)

  • Choi, Yun-Seok;Park, Hyung-Kun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.7C
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    • pp.627-634
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    • 2007
  • When a higher-order modulation scheme (16QAM or 64QAM) is applied to the communications system using the nonlinear high power amplifier (HPA), the performance can be degraded by the nonlinear distortion of the HPA. The nonlinear distortion can be compensated by the adaptive nonlinear Volterra equalizer using the low-complexity LMS algorithm at the receiver. However, the LMS algorithm shows very slow convergence performance. So, in this paper, the parallel M-band discrete wavelet transformed LMS algorithm is proposed in order to improve the convergence speed. Throughout the computer simulations, it is shown that the convergence performance of the proposed method is superior to that of the conventional time-domain and transform-domain LMS algorithms.

Purification and Characterization of Hpa I endonuclease (Hpa I endonuclease의 정제와 특성)

  • Yoon, Ho Sup;Kang, Sun Chul;Yoo, Ouk Joon
    • Microbiology and Biotechnology Letters
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    • v.13 no.1
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    • pp.87-91
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    • 1985
  • Hpa I endonuclease from Haemophilus parainfluenzae has been purified of homogeneity and its physical and ezymatic properties have been studied. For the purification of the enzyme, Heparin agarose, SP-sephadex C-25, DEAE-sephadex A-50 and phosphocellulose chromatography columns were used. The denatured and reduced form of the enzyme is a monomer of molecular weight of $30,000{\pm}1,000$ as judged by 10% polyacrylamide gel electrophoresis containing 0.1% sodium dodesyl sulfate. Hpa I endonuclease was maximally active at neutral pH (7.0 to 7.5) in the presence of 50 mM NaCl.

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Nonlinear Effect on the BER and Spectrum Shape of OFDM, UFMC and FBMC for 5G Mobile Communication (5세대 이동통신을 위한 OFDM, UFMC, FBMC 시스템의 BER과 스펙트럼의 비선형 특성 평가)

  • Lee, Dong-Hyung;An, Changyoung;Kung, Kyung-Lok;Kim, Byeongjae;Ryu, Heung-Gyoon
    • Journal of the Institute of Electronics and Information Engineers
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    • v.53 no.6
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    • pp.3-14
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    • 2016
  • Recently, researches for new waveforms have been carried in order to satisfy KPI for 5G mobile communication system. UFMC and FBMC are well known as ways to reduce OOB power. In this paper, we analyze spectrum of OFDM, UFMC, and FBMC system under nonlinear HPA environment. And then we evaluate and analyze performance of these systems under the same environment. As simulation results, OOB power of OFDM, UFMC, and FBMC increases with HPA nonlinearity increasement. Especially, OOB power of FBMC is the largest increase due to HPA nonlinearity. Also, BER performance of these systems is degraded by increasement of HPA nonlinearity. Therefore, In this paper, we can confirm that a system with low-complexity and high-speed processing is advantageous, because BER performance and OOB power characteristic of these systems are degraded to similar level, when these systems are implemented in real world.

Design and Analysis of 4D-8PSK-TCM System Considering the Nonlinear HPA Environment (비선형 HPA 환경을 고려한 4D-8PSK-TCM 시스템의 설계 및 분석)

  • An, Changyoung;Ryu, Sang-Burm;Lee, Sang-Gyu;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.29 no.4
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    • pp.299-307
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    • 2018
  • Considering a nonlinear high power amplifier(HPA) and a predistorter, we have designed a four-dimensional 8-ary phase shift keying trellis-coded modulation(4D-8PSK-TCM) system, which is recommended for X-band satellite communications. Subsequently, we have evaluated and analyzed the spectrum, constellation characteristics, and BER performance of the system. In satellite communications, owing to the limited power, nonlinear characteristics that determine the operating point of the HPA must be analyzed because the HPA consumes high power. We herein report the design of the 4D-8PSK-TCM system, with efficiencies of 2 and 2.25 bits/channel-symbol. The simulation results confirmed that a 0.35 roll-off value is effective, considering the low peak-to-average power ratio(PAPR) characteristic and the narrow occupation bandwidth of the spectrum. It also confirmed that approximately 15~20 dB of output backoff(OBO) value is required at the HPA when the predistorter is not used, and approximately 1 dB of the OBO value is required when the predistorter is used.

Pre-distorter Method Using LUT with 2ι Partition Interpolation in the OFDM System (OFDM 시스템에서 2ι 분할 보간을 LUT에 결합한 전치왜곡기에 관한 연구)

  • 권오주;이호근;하영호
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.27 no.7A
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    • pp.668-675
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    • 2002
  • This paper proposes pre-distorter combined LUT with 2ιpartition interpolation method to reduce nonlinear distortion which was caused by high PAPR and to update LUT quickly. Pre-distorted gain and phase can be found by using LUT which consisted of AM/AM and AM/PM value, and OFDM signal amplitude. The proposed 2ιpartition interpolation can accurately find predistorted gain and phase using bit shift and add component instead of increasing size of LUT which requires increasing the amount of computation. The performance of the proposed method was measured by the difference between HPA input and output characteristics by the LUT size, constellation, SER performance by the HPA, and LUT update error by the HPA characteristic changes. As a result, it is shown that when the size of the LUT is 32 and 64 for 16-QAM and 64-QAM, nonlinear distortion nearly didn't occurred.

Compensation for Nonlinear Distortion in OFDM Systems Using a Digital Predistorter Based on the Canonical PWL Model (Canonical PWL 모델 기반의 디지털 사전왜곡기를 이용한 OFDM 시스템의 비선형 왜곡 보상)

  • Seo, Man-Jung;Shim, Hee-Sung;Im, Sung-Bin;Jung, Jae-Ho;Lee, Kwang-Chun
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.1C
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    • pp.65-76
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    • 2010
  • Orthogonal frequency division multiplexing (OFDM) is an attractive technique for achieving high-bit-rate wireless data transmission. However, multicarrier systems such as OFDM show great sensitivity to nonlinear distortion. The OFDM structure requires a summation of a large number of subcarriers for multicarrier modulation, and as a result of this summation large signal envelope fluctuations occur. These fluctuations make OFDM systems to be very sensitive to nonlinear distortion introduced by the high power amplifier (HPA) at the transmitter. In this paper, we propose a canonical piecewise-linear (CPWL) model based digital predistorter to compensate for nonlinear distortion introduced by the high peak-to-average power ratio (PAPR) and the HPA in OFDM systems. The performance of the new predistortion scheme for OFDM systems is evaluated in terms of total degradation (TD) and bit error rate (BER). The simulation results demonstrated that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinear distortion introduced by the HPA.

Improvement of Power Efficiency of HPA by the PAPR Reduction and Predistorter in MIMO-OFDM (MIMO-OFDM에서 PAPR 저감 및 사전 왜곡기에 의한 HPA의 전력 효율 개선)

  • Trang Ngo Thi Thu;Kim Nam;Han Tae-Young
    • The Journal of the Korea Contents Association
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    • v.5 no.1
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    • pp.201-208
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    • 2005
  • Tn this paper, we evaluate the peak-to-average power ratio (PAPR) performance in a space-time block code (STBC) multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) system using selected mapping (SLM) and partial transmit sequences (PTS) approaches. SLM and PTS methods are used to decrease the nonlinear distortion and to improve the power efficiency of the nonlinear high power amplifier(HPA) in the MIMO-OFDM system. In simulation result, when compared with the existing MIMO-OFDM system using QPSK, the PTS method reduces the PAPR about 5dB while the SLM method can reduce about 3.5 dB. Also, we find the BER performance of the MIMO-OFDM system with and without the predistorter in front of the HPA. When the predistorter is used, the input back-off (IBO) of 4 dB is required in the PTS method, and IBO of 6 dB in the SLM method to closely conform to the linear amplifier. If the method of improving the PAPR is not used, the value of IBO of 8 dB is required.

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