| 摘要: | 論文提要 近年來，全球行動通信系統(GSM，Global System for Mobiles)技術已普遍應用在各國行動通訊系統上；雖然大多數的GSM系統已架設許多基地收發站(BTS，Base Transceiver Station)於蜂巢網中，但在某些區域，收發信號仍無法涵蓋某些角落；為了涵蓋偏遠地區如山谷及較大的區域如超高大樓及地下隧道，須在這些區域安裝一個簡單而經濟的光纖強波器(fiber repeater)，來提升信號的強度，可改善現有通信網路之通話品質。 此類強波器基本上分成二部份，第一部份為主機部份(MU，Master Unit)，其功能為將下鏈(DL，Downlink)信號對雷射光做調變而後送入光纖中傳送，同時將上鏈(UL，Uplink)的光信號由光偵測器轉換成RF信號；第二部份為遠端機部份(RU，Remote Unit)，其功能為對下鏈信號做檢波，並對上鏈信號做調變。使用光纖強波器較不會造成熱雜訊過度放大的問題，故在光纖系統中的信號雜訊比值比傳統的系統有更好的效果。 文內除了已建構光纖強波器基本電路架構與分析電路工作原理，並特別設計每個基本模組，使系統之三階交互調變、輸出功率、三階交叉點及鏈路預算、......等特性符合GSM11.26規範中之規格，且在某些重要參數超越現有的系統如Yutaka Fuke 、R. E. Schuh、Yoshio Ebine。我們也對雷射二極體做預失真處理，使用低價格元件傳送高功率信號至10dBm而不失真的將信號放大,可填補細胞中的盲區,擴大覆蓋通訊範圍。 Abstract: In recent years, GSM systems have been deployed using many base transceiver stations (BTS) in many countries. However, in some areas, such as basements of buildings, tunnels and valleys, there may be no signal, and in some regions fading may occur. These problems can be solved cheaply by implementing fiber repeaters to strengthen the signals for the coverage of rural region such as valleys and bigger region such as high buildings and tunnels. A fiber repeater is consisted of two parts. The first part is the master unit (MU), which uses the downlink (DL) RF signal to modulate the laser light transmitted through fiber and uses the photodiode to detect out the up link (UL) RF signal. The second part is the remote unit (RU), which detects the DL RF signal and modulates the UL laser light. A fiber repeater amplifies less thermal noise, so the signal-to-noise-ratio is better than a traditional repeater. This article delineates the constructing of the basic circuits of a fiber repeater, analyzing the theorems of the circuits and specially designing every module, ensure the performances of system such as third order inter-modulation, output power, third order intercept point and link budget etc. meet the specifications of GSM11.26 standard. Some performances of our fiber repeater are better than the systems of Yutaka Fuke 、R. E. Schuh、Yoshio Ebine. We also developed the pre-distortion method of laser diode, using cheap laser diode transmit the RF signal up to 10dBm without distortion. Such fiber repeater is suited for amplifying the signals in valleys, high buildings and tunnels, reducing the blind regions of cells and expanding the coverage areas of communication. |
