• Title/Summary/Keyword: Nonlinear HPA

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Performance analysis on the nonlinear distortion in OFCDM downlink system using clipped multilevel-PSK (Clipped multilevel-PSK를 이용한 OFCDM 순방향 링크에서 비선형 왜곡에 대한 성능 분석)

  • 안치훈;최영관;장승훈;김동구
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.40 no.11
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    • pp.17-26
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    • 2003
  • To reduce the nonlinear distortion of high power amplifier(HPA) in down link OFCDM system to employ time domain spreading, we apply technology which transmits MPSK(Multilevel-PSK) signal after clipping on multilevel input signal of IFFT subcarrier. In case that the nonlinear distortion of HPA is considered in AWGN channel, performacne of clipping OFCDM system using extended m sequence is over 2.2㏈ better than that of OFCDM system using extended m sequence when the number of user is 8 and 16. In case that the nonlinear distortion of HPA is considered in quasi-static channel, performacne of clipping OFCDM system using extended m code is over 2㏈ better than that of OFCDM system using extended m sequence when the number of user is 8 and 16.

A SCPWL Model-Based Digital Predistorter for Nonlinear High Power Amplifier Linearization (비선형 고출력 증폭기의 선형화를 위한 SCPWL 모텔 기반의 디지털 사전왜곡기)

  • Seo, Man-Jung;Jeon, Seok-Hun;Im, Sung-Bin
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.47 no.10
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    • pp.8-16
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    • 2010
  • An orthogonal frequency division multiplexing (OFDM) system is a special case of multicarrier transmission, where a single data stream is transmitted over a number of lower-rate subcarriers. One of the main reasons to use OFDM is to increase robustness against frequency-selective fading or narrowband interference. However, in the radio systems the distortion introduced by high power amplifiers (HPA's) such as traveling wave tube amplifier (TWTA) considered in this paper, is also critical. Since the signal amplitude of the OFDM system is Rayleigh-distributed, the performance of the OFDM system is significantly degraded by the nonlinearity of the HPA in the OFDM transmitter. In this paper, we propose a simplicial canonical piecewise-linear (SCPWL) model based digital predistorter to compensate for nonlinear distortion introduced by an HPA in an OFDM system. Computer simulation is carried on an OFDM system under additive white Gaussian noise (AWGN) channels with 16-QAM and 64-QAM modulation schemes and modulator/demodulator implemented with 1024-point FFT/IFFT. The simulation results demonstrate that the proposed predistorter achieves significant performance improvement by effectively compensating for the nonlinearity introduced by the HPA.

A Design of High Power Amplifier Predistortor using Carrier Complex Power Series Analysis (Carrier Complex Power Series 해석을 통한 대전력 증폭기용 전치 왜곡기 설계)

  • 윤상영;정용채
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.12 no.5
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    • pp.686-693
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    • 2001
  • In this paper, a new carrier complex power series which represents nonlinear transfer function of high power amplifier is derived. Using this transfer function, the nonlinear transfer function of predistortive circuit for linearizing the distortion effect of a HPA(High Power Amplifier) is derived and fabricated. A measured gain and $P_{1dB}$ of the fabricated HPA in IMT-2000 basestation transmitting band are 34.06 dB and 35.4 dBm. The predistortive circuit using inverse carrier complex power series is fabricated and operated with HPA. The predistortive HPA improves C/I(Carrier to Intermodulation) ratio of HPA by 17.01 dB(@Pout=25.43 dBm/tone) with 2-tone at 2.1375 GHz and 2.1425 GHz.

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Adaptive Predistortion for High Power Amplifier by Exact Model Matching Approach

  • Ding, Yuanming;Pei, Bingnan;Nilkhamhang, Itthisek;Sano, Akira
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.401-406
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    • 2004
  • In this paper, a new time-domain adaptive predistortion scheme is proposed to compensate for the nonlinearity of high power amplifiers (HPA) in OFDM systems. A complex Wiener-Hammerstein model (WHM) is adopted to describe the input-output relationship of unknown HPA with linear dynamics, and a power series model with memory (PSMWM) is used to approximate the HPA expressed by WHM. By using the PSMWM, the compensation input to HPA is calculated in a real-time manner so that the linearization from the predistorter input to the HPA output can be attained even if the nonlinear input-output relation of HPA is uncertain and changeable. In numerical example, the effectiveness of the proposed method is confirmed and compared with the identification method based on PSMWM.

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Compensation for Nonlinear RE Power Amplifier using a Variable Step-Size LMS algorithm

  • Kim, Hyoun kuk;Park, Ke young;Lee, Yong min
    • Proceedings of the IEEK Conference
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    • 2002.06a
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    • pp.153-156
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    • 2002
  • An adaptive predistorr is proposed to compensate for the nonlinear distortion of a high power amplifier (HPA) in 16 QAM system. It fumed out that the proposed predistorter using a variable step-size least mean square (VSSLMS) algorithm is stable and can reduce the Total Distortion (TD) to 0. 1dB at the HPA output backoff=0.0 dB.

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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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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.

Relation between IBO and BER in the OFDM Communication System using Predistorter for the Nonlinear Compensation (비선형 보상을 위하여 Predistorter를 사용한 OFDM 통신 시스템에서 IBO와 BER의 관계)

  • 박주석;이강미;유흥균
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.15 no.7
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    • pp.692-697
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    • 2004
  • OFDM system is very useful for the multi-path channel and highly bandwidth-efficient system. However, OFDM signal shows the high PAPR so that nonlinear distortion can happen in the HPA(high power amplifier). This paper studies BER performance variation according to IBO(input back off) values when the predistorter is used fur the compensation for the HPA nonlinearity. In case of the SSPA(solid state power amplifier) of nonlinearity parameter p=0.5 and IBO=0㏈, the system with predistorter is poorer than the one without predistorter. But this situation is inverted, if IBO is increased from 0㏈ to 3㏈. So, we can find that there is a threshold value of IBO for the predistorter to effectively compensate for the nonlinear SSPA when the sub-carrier number and p value are changed.

Design and Performance Evaluation of Receiver Feedback Closed Loop Pre-Distortion System (수신기 포함 폐루프 전치왜곡기 설계와 성능 평가)

  • Bok, Junyeong;Jo, Byung Gak;Baek, Gwang Hoon;Ryu, Heung-Gyoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37A no.10
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    • pp.827-833
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    • 2012
  • The receiver performance is degraded by nonlinear memory problem in communication system. The pre-distorter techniques are an effective technique to compensate for the nonlinear distortion of the HPA without memory effects. However, memory effect of HPA can no longer be ignored when data signal is transmitted in high speed. Many adaptive pre-distorter schemes have been studied to compensate for memory effect problem of HPA in transmitter. The complexity and cost of satellite will increase when using adaptive pre-distorter in satellite communication system. In this paper, we propose receiver feedback closed loop pre-distortion technique in order to compensate for nonlinear problem of HPA with memory problem. The purpose of this paper is to reduce complexity and cost of satellite design by using only pre-distorter at terrestrial station.

Power and Spectrum Efficiencies Considering the HPA Nonlinearity in OFDM Communication System (OFDM 통신 시스템에서 비선형 증폭기 특성을 고려한 전력 효율과 대역 효율)

  • 이재은;윤기후;이준서;유흥균
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.14 no.6
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    • pp.543-549
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    • 2003
  • It is important to consider the nonlinear effects of the HPA(High Power Amplifier) in the OFDM communication systems and other digital communication systems as well. In this paper, we investigate a new performance figure-of$.$merit(D) that reflects both power and spectrum efficiencies. The performance figure-of-merit is expressed to include the spectrum and power efficiencies that depend on the magnitude of IBO(Input Backoff) and the number of subcarriers. So, we analyze the variation characteristics of the power efficiency and spectrum efficiency which has the tradeoff relationship.