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4、atingpersonnelbeforetakingoverandshiftbeforethejurisdictionareatoconductacomprehensiveinspectionofequipment,runningthesquadlea移动通信中频分复用技术的分析和研究频分多路复用系统的信道复用率高,分路方便,因此目前模拟通信中常采用这种复用方式,特别是在有线和微波通信系统中应用广泛。一、原理研究和分析1、频分复用的原理复用是指将若干个彼此独立的信号合并成可在同一信道上传输的复合信号的方法,常见的信号复用采用按频率区分与按时间区分的方式,前者称为频分
5、复用,后者称为时分复用。通常在通信系统中,信道所提供的带宽往往比传输一路信号所需要的带宽宽得多,这样就可以将信道的带宽分割成不同的频段,每频段传输一路信号,这就是频分复用(frequencydivisionmultipleaccess)(FDMA)。为此,在发送端首先要对各路信号进行调制将其频谱函数搬移到相应的频段内,使之互不重叠。再送入信道一并传输。在接收端则采用不同通带的带通滤波器将各路信号分隔,然后再分别解调,恢复各路信号。调制的方式可以任意选择,但常用的是单边带调制。因为每一路信号占据的频段小,最节省频带,在同一信道中传送的路数可以增加。图1频分复用系统的示
6、意图图1给出了频分复用系统的示意图。如图所示,其中f1(t),f2(t),…,fn(t)习总书记在梁家河工作生活的那段岁月中,即使条件再艰苦、劳动再繁忙、书籍再有限,都废寝忘食的不忘读书,先后阅读了《共产党宣言》《国家与革命》《资本论》等马列经典著作、《中世纪史》《史记选》《中国古代思想是》derondutyduringmajorequipmentoverhaul,beforeandaftertheshifttodesignatedstafftounderstandtheoperationofequipmentintheequipmentandcheckonfocu
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