干線(xian)(xian)放(fang)大(da)器(qi)是(shi)主干線(xian)(xian)纜(lan)(lan)(lan)傳輸鏈(lian)路(lu)上的雙(shuang)向信號(hao)(hao)處理放(fang)大(da)設(she)(she)備(bei)(bei)。當主干線(xian)(xian)纜(lan)(lan)(lan)傳輸距離長，或鏈(lian)路(lu)中負載(zai)器(qi)件數量較多，雙(shuang)向信號(hao)(hao)損耗(hao)過大(da)，來自信號(hao)(hao)源（下(xia)行(xing)）或來自天線(xian)(xian)（上行(xing)）的信號(hao)(hao)強度偏(pian)低，相關指(zhi)標將(jiang)不能滿足設(she)(she)計(ji)的技術要(yao)求，將(jiang)直接(jie)(jie)影響到(dao)室內天線(xian)(xian)的端口發(fa)射功率和(he)基站接(jie)(jie)收(shou)機（中繼臺)）的端口的接(jie)(jie)收(shou)功率，這就(jiu)必(bi)須在主干線(xian)(xian)纜(lan)(lan)(lan)傳輸鏈(lian)路(lu)中的適(shi)當位置增加干線(xian)(xian)放(fang)大(da)器(qi)設(she)(she)備(bei)(bei)。

干線放(fang)大(da)(da)器具有雙(shuang)向信(xin)號(hao)放(fang)大(da)(da)功(gong)(gong)能，上行(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)信(xin)號(hao)處理及放(fang)大(da)(da)電路獨立(li)分開，上行(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)放(fang)大(da)(da)功(gong)(gong)率(lv)可單(dan)獨調(diao)節(jie)，可根據實(shi)際(ji)要求進(jin)行(xing)(xing)(xing)現場測驗(yan)后對上行(xing)(xing)(xing)/下(xia)(xia)行(xing)(xing)(xing)信(xin)號(hao)增益進(jin)行(xing)(xing)(xing)分別設置，這樣極大(da)(da)地(di)方便(bian)了系統調(diao)試，從(cong)而(er)更有效地(di)保證了系統的安(an)全穩(wen)定(ding)性和(he)建(jian)筑(zhu)物內電磁環(huan)境(jing)滿足國家有關標準(zhun)。