s06-03.htm

扩频通信讲座

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            自同步法，也称同步信息提取法。</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'">这种方法是利用发端发送的数字信息序列中隐含的同步信息，在接收端将其提取出来从而获得同步信息实现跳频。此法不需要专门的信道和发送专门的同步码字，所以它具有节省信道、节省信号功率和同步信息隐蔽等优点。</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'">上述三种基本的同步信息传递方法各有利弊。</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'">独立信道法需要专门的信道来传送专门的同步信息，因此它占用频率资源和信号功率。另外，其同步信息传送</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'">方式不隐蔽，易于被敌方发现和干扰。其优点是传送的同步信息量大，同步建立的时间短，并能不断地传送同步信息，保持系统的长时问同步。</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'">同步字头法虽然不需专门的同步信息信道而是利用通信信道来传送同步信</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">息，它还是挤占了通信信道频率资源和信号功率。所以它的缺点与独立信道法相似。为了使同步信息隐蔽，应采用尽量短的同步字头，但是同步字头太短又影响传送的同步信息量的多少，需折衷考虑。采用同步字头法的跳频系统为了能保持系统的长时间同步，还需在通信过程中，插入一定的同步信息码字。</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'">自同步法在节省频率资源和信号功率方面具有优点。但由于发端发送的数字信息序列中所能隐含的同步信息是非常有限的，所以在接收端所能提取的同步信息就更少了。此法只适用于简单跳频图案的跳频系统，并且系统同步建立的时间较长。</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'">在实际的跳频系统中，常常是将这几种基本方法组合起来应用，使跳频系统达到某种条件下的最佳同步。</SPAN></P>
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            lang=EN-US style="FONT-SIZE: 12pt; COLOR: navy">6.3.2<SPAN 
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            style="FONT-SIZE: 12pt; COLOR: navy; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">几种实用的同步方法</SPAN><SPAN 
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            模拟跳频系统的同步方法</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'">模拟跳频系统是指传送模拟信号的跳频通信系统，例如模拟话音信号。那么，在模拟通信系统中如何传送跳频同步信息</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'">回答只能是利用模拟信号携带同步信息。</SPAN><SPAN 
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            </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'">我们知道话音占据的领带在</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'">之间，因此可利用低于</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'">或高于</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'">的频率来传送同步信息。这种方法叫带外单音法。</SPAN><SPAN 
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            </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'">此法是利用</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'">的话音频带，传送用单音进行编码的模拟信号同步字头。比如，用两个单音进行编码，传号时的单音频率是</SPAN><SPAN 
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            style="mso-spacerun: yes">&nbsp; </SPAN>1200Hz</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，空号的频率是</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'">，采用最小频移键控调制方式，便获得带内的同步信息码字。此码字再经过模拟通信系统传送至收端，收端解出同步信息后，按照同步指令实现跳频同步。</SPAN><SPAN 
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            style="FONT-SIZE: 12pt; COLOR: teal; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">数字</SPAN><SPAN 
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            style="FONT-SIZE: 12pt; COLOR: teal; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">跳频系统的同步方法</SPAN><SPAN 
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