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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
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman"><FONT
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(4)</FONT></SPAN></FONT></B></FONT></DIV></TD></TR>
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<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; LINE-HEIGHT: 150%"><B><FONT
color=#800080 size=4><SPAN lang=EN-US>6.4<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">跳频图案的产生</SPAN></FONT><SPAN
lang=EN-US style="FONT-SIZE: 12pt"> <O:P></O:P></SPAN></B></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; LINE-HEIGHT: 150%"><SPAN
lang=EN-US style="FONT-SIZE: 12pt; COLOR: navy">6.4.1<SPAN
style="mso-spacerun: yes"> </SPAN></SPAN><SPAN
style="FONT-SIZE: 12pt; COLOR: navy; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">跳频图案与跳频频率表</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt; COLOR: navy"><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'">跳频图案是由跳频指令控制频率合成器所产生的频率序列。跳频系统中，<BR>跳频带宽和可供跳变的频率</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'">频道</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'">数目都是预先定好的。</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'">比如说，跳频带宽为</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">5MHz</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，跳频频率的数目是</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个，频道间隔是</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">25kHz</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这样，在</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">5MHz</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">带宽内可供选用的频道数远大于</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个，那么你怎样选择出</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个频率来呢</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'">这就是所谓的跳频频率表。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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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'">根据电波传播条件、电磁环境条件以及敌方干扰的条件等因素来制定一张或几张具有</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个频率的频率表，即</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f1</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f2</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，…</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，另一张可以是</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f1</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">’，</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f2’,</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">…</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f64’</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">。如果采用</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f1</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f2</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，…</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">f64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">这张频率表，那么跳频指令发生器则是根据这张频率表向频率合成器发出指令进行跳频的。那么又怎样在这</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个频率中做到伪随机地跳频呢</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">?<SPAN
style="mso-spacerun: yes"> </SPAN><O:P></O:P></SPAN></P>
<P class=MsoNormal
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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'">
这就是由图</SPAN><SPAN lang=EN-US style="FONT-SIZE: 12pt">6</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">－</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">8</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">所示的跳频指令发生器和频率合成器来实现的。跳频指令发生器主要是一个伪码发生器。伪码发生器在时钟脉冲的推动下，不断地改变码发生器的状态。不同的状态对应于一张跳频频率表中的一个频率。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">种状态则对应</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个频率。再根据此频率，按照频率合成器可变分频器、置位端的要求，转换成控制频率合成器的跳频指令。由于伪码发生器的状态是伪随机地变化，所以频率合成器输出的频率也在</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">64</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">个频率点上伪随机的跳变，便生成了伪随机</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt; mso-spacerun: yes">
</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">地跳频图案。当频率表不同时，虽然用同一个伪码发生器，实际所产生的跳频图案也是不同的。</SPAN></P>
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<P class=MsoNormal
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lang=EN-US style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></P>
<P class=MsoNormal
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lang=EN-US style="FONT-SIZE: 12pt; COLOR: navy">6.4.2<SPAN
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