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<TD borderColor=#6699ff><FONT size=2>您的位置：技术园地>技术讲座-扩频通信</FONT></TD></TR>
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<DIV align=center><FONT size=4><B><SPAN
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color=#000080 size=5>第六讲 </FONT></SPAN><FONT size=5><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><SPAN
style="COLOR: #333399; FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">跳频</SPAN><FONT
color=#000080>系统(3)</FONT></SPAN></FONT></B></FONT></DIV></TD></TR>
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<P class=MsoNormal
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color=#800080 size=4><SPAN lang=EN-US>6.3<SPAN
style="mso-spacerun: yes"> </SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">跳频系统的同步</SPAN></FONT><SPAN
lang=EN-US style="FONT-SIZE: 12pt"> </SPAN></B></P>
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<SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">跳频系统的同步是关系到跳频通信能否建立的关键。</SPAN><SPAN
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style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">那么，怎样才能实现通信双方的跳频同步呢</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">? </SPAN></P>
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lang=EN-US style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 24pt; LINE-HEIGHT: 150%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">同步的含义是：跳频图案相同</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">, </SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">跳变的频率序列</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">也称频率表</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">相同，跳变的起止时刻</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">也称相位</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">相同。因此，为了实现收、发双方的跳频同步，收端首先必须获得有关发端的跳频同步的信息，它包括采用什么样的跳频图案，使用何种频率序列，在什么时刻从那一个频率上开始起跳，并且还需要不断地校正收端本地时钟，使其与发端时钟一致。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 24pt; LINE-HEIGHT: 150%"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">根据收端获得发端同步信息和校对时钟的方法不同而有各种不同的跳频同步方式。</SPAN> </P>
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lang=EN-US style="FONT-SIZE: 12pt; COLOR: navy">6.3.1</SPAN><SPAN
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跳频同步信息的基本传递方法</SPAN><SPAN lang=EN-US
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独立信道法。</SPAN><SPAN lang=EN-US
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style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">利用一个专门的信道来传送同步信息；收端从此专门信道中接收发端送来的步信息后，依照同步信息的指令，设置接收端的跳频图案、频率序列和起止时刻，并校准收端的时钟，在规定的起跳时刻开始跳频通信。这种方式，需要专门的信道来传送同步信息，有的通信系统难以提供专门的信道，因此独立信道法的应用受到了限制。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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前置同步法，也称同步字头法。</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt"><O:P>
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style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">在跳频通信之前，选定一个或几个频道上先传送一组特殊的携带同步信息的码字，收端接收此同步信息码字后，按同步信息的指令进行时钟校准和跳频。因为是在通信之前先传送同步码字，故称同步字头法。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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