60-GHz 光載微波無線訊號系統中相位雜訊抑制演算法

Abstract

60 GHz 頻段在這幾天來蓬勃的發展，世界上主要的科技電子公司都投入資源在相關的技術研發上，而由於60 GHz 的無線訊號會被空氣中的水分子吸收的物理特性，所以60 GHz 被定為室內使用的無線架構，但將訊號送至無線基地台的過程中，高頻的同軸電纜太過昂貴，而光載微波訊號系統就成了最好的傳輸系統。在光載微波訊號傳輸系統中，會由於做為訊號載波用的雷射光源的線寬以及光纖的色散現象而產生相位雜訊，而由色散以及雷射線寬所引起的相位雜訊會隨著光纖傳輸距離的增加與雷射線寬的大小的不同而有不同程度的影響並且降低訊號的品質。 在本研究中建立了相位雜訊的模型，並以數位訊號處理的方式降低相位雜訊對於訊號的影響，進而提升訊號的品質或是資料傳輸率。

The demand for the wireless bandwidth is increasing and in near future a few Gbps over wireless will be needed. The best way to provide the such high capacity wireless is over 60 GHz because of the huge 7 GHz unlicensed bandwidth. The radio-over-fiber (RoF) systems provide efficient ways for transportation and distribution of high frequency signals such as 60 GHz. The phase noise (linewidth) laser light source and fiber dispersion in the RoF system will induce the impairment of the signal and limit the transmission distance and data rate. In this research, the phase noise model and mitigation algorithm are built up and reduce the bit-error-rate under the FEC limit through over 100 km transmission and DFB laser. Combine with bit-loading, the data rate can improve over 15% with 100 km fiber transmission.