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標題: OFDM Based Receiver Designs for Next Generation Optical Access Network & Radio over Fiber System(I)
作者: 黃穎聰
關鍵字: OFDM
passive optical network
radio over fiber
optical receiver
base band
optical front end
frequency synthesizer
channel codec
摘要: In this group project, two of the main applications on the emerging optical accessnetwork, i.e, Next Generation Passive Optical Network (NG-PON) and Radio over Fiber(RoF) will be investigated to develop their receiver chip designs. To enhance the spectrumefficiency, orthogonal frequency division multiplexing (OFDM) technique using QAMmodulation will be employed in lieu of the conventional NRZ scheme. The three-yearproject span will be divided into two phases. Phase 1 is mainly devoted to the receiverdesign of NG-PON, an access network designated for the FTTX applications. The key issuesare to reduce the spectrum demand for low cost optical devices, and to mitigate thechromatic dispersion on fiber communication. The tentative specs are 1.66GHz in signalbandwidth, 64 QAM modulation, and 12Gbps/8.82Gbps respectively for raw and effectivedata rates. Phase 2 of the project is to explore the 60 Hz RF wireless receiver for the RoFsystem. Part of the NG-PON receiver module designs will be reused and new endeavors areput on the 60GHz RF module, high speed ADC, channel decoder, and base band DSPsolutions to mitigate optical and wireless channel impairments simultaneously. Tentativespecs indicate a pass band spectrum usage of 2.75 GHz, 16 QAM modulation, and16Gps/9.78Gbps respectively for raw and effective data rates.This group project consists of 5 major topics, i.e. base band, front end & RF, PLL &frequency synthesizer, ADC, and channel decoder. Owing to a 4GSps 6-bit wide data streamfrom the ADC, the base band design features a highly parallel architecture to cope with thethroughput requirement. The channel decoder, consisting of both LDPC and Reed Solomonnodules, is expected to yield a coding rate as high as 10dB while maintaining the throughput.The front end module consists of TIA and VGA circuits interfacing with optical devices. TheRF module contains LNA, mixer and frequency synthesizer capable of working at the rangeof 60 GHz. To ensure seamless integration among these modules, a top down designapproach is adopted. Starting with the entire system performance specs and link budget, thefunction and interface specs of each module are derived accordingly. Elaborate test plans aredeveloped in advance before the chip designs so that all possible testing or interfaceproblems can be ironed out in the first place. The developed NG-PON receiver design isexpected to integrate with an optical test bed for real time processing. Integration among theRoF receiver modules will be pursued as well.
本計畫主要是針對日趨普及的光纖接取系統,根據未來兩個主要的應用,也就是下世代被動式光纖接取網路(Next Generation Passive Optical Network, NG-PON)與光載射頻系統(Radio over Fiber, RoF),設計其接收機晶片。而為了增加傳輸訊號的頻譜使用效率,進而提升整體資料傳輸速率,我們將摒棄目前光纖傳輸上常用的Non-Return-Zero (NRZ) format,而以正交分頻多工(Orthogonal Frequency DivisionMultiplexing, OFDM)傳送Quadrature Amplitude Modulation (QAM)訊號的方式來實現。計畫將以三年期分成兩個phase 來完成個別接收機晶片之設計。Phase 1 將執行NG-PON 之設計,其主要應用係針對FTTx 等級之接取電路。重點在以OFDM 方式降低光電元件的成本,並補償光纖傳送的色散問題。NG-PON 預計使用1.66GHz 訊號頻寬,採64QAM 調變方式,預期的raw/effective data rate 可分別達到12Gbps/8.82Gbps。Phase 2 則是針對傳送60GHz RF 訊號的RoF 系統 wireless receiver 來設計。除了將Reuse NG-PON 的部分OFDM 模組設計外,重點在於60GHz 的RF 模組、高速ADC及channel decoder 設計以及如何利用base band DSP 來同時解決光纖及無線通道的干擾問題。預計規格是使用約2.75GHz 的傳輸頻寬(double side band),以較保守的16QAM調變方式,,預期的raw/effective data rate 可達到16Gps/9.78Gbps。本群體計畫一共涵蓋了五個子計畫主題,分別是1)基頻設計 2)前端及射頻電路電路 3)鎖相迴路與頻率合成器 4) 類比數位轉換器,以及5)通道邊解碼器。由ADC提供4GHz 6-bit resolution 的取樣,基頻電路以一高度平行化的設計來降低其工作頻率。通道解碼器包含了LDPC 以及RS 兩種coding,必須以極高的速率完成,並達到10dB 的編碼增益。前端電路是和光元件接軌,主要是轉阻放大器以及可調式增益放大器等。60GHz RF 模組則涵蓋了高效能的LNA、mixer 以及頻率合成器。為了確保各子計畫的模組能順利的整合,我們從整個系統的效能規範與鍊結預算開始,完整的定義每個模組的功能與界面規格。並且擬定了詳細的測試以及晶片整合規劃。預計NG-PON的設計將與optical test bed 實際結合測試,而RoF 的部分也將有分別整合的數位與RF的晶片模組。
其他識別: NSC99-2221-E005-109
Appears in Collections:電機工程學系所



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