• Title/Summary/Keyword: Predistortion

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Predistortion for Frequency-Dependent Nonlinearity of a Laser in RoF Systems

  • Najarro, Andres C.;Kim, Sung-Man
    • Journal of information and communication convergence engineering
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    • v.14 no.3
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    • pp.147-152
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    • 2016
  • In radio-over-fiber (RoF) systems, nonlinear compensation is essential to improve performance. Among the several existing nonlinear compensation techniques, we investigate a predistortion technique for a directly modulated laser in an RoF system. First, we obtain the input-to-output response of a directly modulated laser at 160, 820, and 1,540 MHz. The results show that the laser response is dependent on the frequency band. Second, we design an optimal predistortion circuit to compensate for the nonlinear responses of three frequency bands. We design the predistortion circuit with two options: each predistortion circuit for each frequency band and one single predistortion circuit for all the three frequency bands. Finally, we present the simulation results of the predistortion system obtained using a commercial simulator. These results show that the third intermodulation distortion (IMD3) is improved by 0.6-9 dB for the three frequency bands with only a single predistortion circuit.

Quality Assessment and Predistortion Evaluation of the Multi-channel Audio Codec according to the bitrate changing (압축율 변화에 따른 멀티채널 오디오의 품질 및 Predistortion 의 영향 평가)

  • Cha, Kyung-Hwan;Jang, Dae-Young;Kim, Sung-Han;Kim, Chun-Duck
    • The Journal of the Acoustical Society of Korea
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    • v.15 no.2
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    • pp.55-60
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    • 1996
  • This paper describes the subjective assessment of the multi-channel audio quality according to the bitrate changing and evaluates the predistortion effect to avoid the unmasked noise after matrixing/dematrxing process in transmission and regeneration of the multi-channel audio. The simulation is processed by the perceptual coding that is MPEG-2 Audio layer II algorithm. We evaluate the quality improvement about predistortion using or not by 384, 320, 256, 128kbps. As the result of the double blind subjective assessment, 5 Grade-Impairment Scale is scored under minus one to 320kbps and so audio quality is evaluated to be perceptible, but not annoying in 3/2 channel. The effect of the predistortion is improved one level in 128kbps and especially speech test material I better improved than music test materials.

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A New Polynomial Digital Predistortion Method Based on Direct Learning for Linearizing Nonlinear Power Amplifier (비선형 앰프의 선형화를 위한 다항식 기반 직접 학습 방식의 디지털 사전왜곡 기법)

  • Jeong, Eui-Rim
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.12
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    • pp.2382-2390
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    • 2007
  • A new polynomial-based predistortion method for linearizing nonlinear power amplifier is proposed. The proposed method finds the predistortion parameter directly without the help of postdistorter whereas most existing polynomial-based predistortion methods calculate the predistortion parameter indirectly from the prostdistorter. First, a new predistortion algorithm is derived based on the assumption that the characteristic of the amplifier is modeled by piecewise linear function. Then it is modified into a proposed method which does not require any assumption or prior knowledge of the amplifier. The proposed method is derived based on the RLS (recursive least squares) algorithm. The proposed technique is simpler to implement than the existing methods and the computer simulation demonstrates that the proposed method is more robust to the initial condition and the saturation region of the amplifier.

Simple Amplitude and Phase Predistortion for PAPR Reduction in OFDM Systems

  • Park, Jeong-Sang;Lee, Jae-Kwon;Kim, Jin-Up
    • ETRI Journal
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    • v.29 no.2
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    • pp.231-233
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    • 2007
  • One of the drawbacks in an OFDM system is the high peak-to-average power ratio (PAPR). Among a number of techniques to reduce the high PAPR, simple amplitude predistortion (SAP), a form of active constellation extension, has been proposed to effectively achieve the desired PAPR. In this letter, a novel scheme, simple amplitude and phase predistortion (SAPP), is proposed. In SAP the carriers' amplitude is utilized to combat the peak signal. Each amplitude is amplified according to its degree of contribution as a metric. In addition to amplitude, SAPP also utilizes the phase. Simulation results indicate that the proposed scheme provides better PAPR reduction than SAP.

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Systematic Design and Realization of opto-electrical Predistortion Optical Transmitter based on Microwave Circuit Modeling for Radio-over-Fiber Systems (유무선 통합시스템을 위한 마이크로파 회로 모델링 기반의 광전자 프리디스토션 광송신기의 설계 및 제작)

  • Lee, Tae-Kyeong;Kim, Hong-Seung;Oh, Guem-Yoon;Kim, Doo-Gun;Choi, Young-Wan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.60 no.4
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    • pp.823-828
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    • 2011
  • We have systematically designed and experimentally demonstrated the opto-electrical predistortion optical transmitter using microwave circuit modelling for reducing the nonlinearity of the distributed-feedback laser diode (DFD-LD). The DFB-LD is analyzed using microwave circuits model based on rate equations. Through the system-level simulation for predistortion method, the optimized characteristics of the RF components in the system are confirmed. The simulated and experimental results show the reduced distortion products. These results are analyzed as the evaluation parameters for the miniaturization and optimization of the opto-electrical predistortion method in radio-over-fiber systems.

Analog Predistortion High Power Amplifier Using Novel Low Memory Matching Topology

  • Kim, Jang-Heon;Woo, Young-Yun;Cha, Jeong-Hyeon;Hong, Sung-Chul;Kim, Il-Du;Moon, Jung-Hwan;Kim, Jung-Joon;Kim, Bum-Man
    • Journal of electromagnetic engineering and science
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    • v.7 no.4
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    • pp.147-153
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    • 2007
  • This paper represents an analog predistortion linearizer for the high power amplifier with low memory effect. The high power amplifier is implemented using a 90-W peak envelope power(PEP) LDMOSFET at 2.14-GHz and an envelope short matching topology is applied at the active ports to minimize the memory effect. The analog predistortion circuit comprises the fundamental path and the cuber and quintic generating circuits, whose amplitudes and phases can be controlled independently. The predistortion circuit is tested for two-tone and wide-band code division multiple access(WCDMA) 4FA signals. For the WCDMA signal, the adjacent channel leakage ratios(ACLRs) at 5 MHz offset are improved by 12.4 dB at average output powers of 36 dBm and 42 dBm.

A Study on the Performance Enhancement of OFDM-Based VLC System by Using Predistortion (전치왜곡을 이용한 OFDM 가시광통신 시스템의 성능개선에 관한 연구)

  • Lee, Dae-Chun;Choi, Kyung-Mook;Park, Young-Il
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.36 no.6A
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    • pp.587-591
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    • 2011
  • In a visible light communication (VLC) system using LEDs, its nonlinearity degrades the performance. If it is compensated by using predistortion and LED's linear range is extended, then a large signal can be used as an LED input and the performance of VLC will be improved. In this paper, a predistortion curve is made by periodic measurement of LED nonlinearity, and the experimental results of predistorted OFDM is provided.

Linearity Improvement of Class E Amplifier Using Digital Predistortion (디지털 사전왜곡을 이용한 마이크로파 E급 증폭기의 선형성 개선)

  • Park, Chan-Hyuck;Koo, Kyung-Heon
    • 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.

A Predistortion Linearizer which is composed of common-gate MESFET circuits (공통 게이트 회로로 구성된 MESFET 전치왜곡 선형화기)

  • Jeung, Seung-Il;Kim, Han-Suk;Kang, Jeung-Jin;Lee, Jong-Arc
    • Journal of IKEEE
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    • v.4 no.2 s.7
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    • pp.241-248
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    • 2000
  • A linear power amplifier is particular emphasized on the CDMA system using a linear modulation scheme, because intermodulation distortion which cause adjacent channel interference and co channel interference is mostly generated in a nonlinear power amplifier. In this paper, a new type of linearization technique proposed. It is presented that balanced MESFET predistortion linearizer added. Experimental result are present for Korea PCS(Personal Communication Service) frequency band. The implemented linearizer is applied to a 30dBm class A power amplifier for simulation Performance. The predistortion linearizer improves the 1dB compression point of the HPA about 2dBm, and intermoudulation distortion about 12.5dBc.

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A Study on the Predistortion Linearizer Controlled by the Individual Order with Frequency Multiplier (주파수 체배기를 이용한 개별 차수 조정 전치왜곡 선형화기의 설계 및 구현)

  • 민준기;이기학;이근태;안창돈;홍의석
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.28 no.12A
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    • pp.1019-1024
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    • 2003
  • In the thesis, we propose a new type of the predistortion linearizer using frequency multiplier The linearizer utilizing the 2nd and 3th harmonic used the individual control of the 3rd and 5th order intermodulation distortion(IMD) component. This structure is composed of wilkinson power combiner for combine and isolation of output signal, 3rd order IMD product controller using doubler and 5th order IMD product controller using tripler. The proposed predistortion linearizer controlled by individual order is obtained for about -16 dBc and 18 dBc of 3rd order and 5th order IMD components, respectively, over the frequency band 870 MHz to 880 MHz at the output power of 34 dBm/tone.