干(gan)線(xian)放大器是(shi)主(zhu)干(gan)線(xian)纜傳輸(shu)鏈路上(shang)的(de)(de)雙(shuang)向(xiang)信號處(chu)理放大設備。當主(zhu)干(gan)線(xian)纜傳輸(shu)距離長(chang)，或(huo)鏈路中(zhong)(zhong)(zhong)負(fu)載(zai)器件(jian)數(shu)量較多(duo)，雙(shuang)向(xiang)信號損耗過大，來自信號源（下行）或(huo)來自天(tian)線(xian)（上(shang)行）的(de)(de)信號強度偏低，相關指標將(jiang)不能滿足設計的(de)(de)技(ji)術要求，將(jiang)直接影響到(dao)室內(nei)天(tian)線(xian)的(de)(de)端(duan)口發射功(gong)(gong)率和基站接收(shou)機（中(zhong)(zhong)(zhong)繼臺(tai))）的(de)(de)端(duan)口的(de)(de)接收(shou)功(gong)(gong)率，這就(jiu)必須在主(zhu)干(gan)線(xian)纜傳輸(shu)鏈路中(zhong)(zhong)(zhong)的(de)(de)適(shi)當位置增加干(gan)線(xian)放大器設備。

干線(xian)放(fang)(fang)大(da)(da)器(qi)具有雙向信(xin)號放(fang)(fang)大(da)(da)功能，上(shang)行(xing)(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)(xing)信(xin)號處理(li)及放(fang)(fang)大(da)(da)電路(lu)獨(du)立分開，上(shang)行(xing)(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)(xing)放(fang)(fang)大(da)(da)功率可單(dan)獨(du)調(diao)節(jie)，可根據(ju)實際(ji)要求進(jin)行(xing)(xing)(xing)(xing)現場測(ce)驗后對上(shang)行(xing)(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)(xing)信(xin)號增益進(jin)行(xing)(xing)(xing)(xing)分別設置，這樣極大(da)(da)地(di)(di)方(fang)便(bian)了系統(tong)調(diao)試(shi)，從而更有效地(di)(di)保(bao)證了系統(tong)的(de)安全穩(wen)定性(xing)和建(jian)筑物內電磁環(huan)境(jing)滿足(zu)國家有關(guan)標準。