s03.htm

扩频通信讲座

            </SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">扩频通信是唯一能够工作于负信噪比条件下的通信方式。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><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'">对于宽带干扰和脉冲干扰在扩频设备中如何被抑制的物理过程，可以用图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.1</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.2</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">加以说明。</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'">对于各种形式人为的</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'">如电子对抗中</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'">干扰或其他窄带或宽带</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'">扩频</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'">系统的干扰，</SPAN><SPAN 
            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'">只要波形、时间和码元稍有差异，解扩后仍然保持其宽带性，而有用信号将被压缩，见图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.1</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。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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            lang=EN-US style="FONT-SIZE: 12pt"></SPAN>&nbsp;</P>
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            align=center><IMG height=158 src="s03.files/t5.gif" width=500 
            border=0><SPAN lang=EN-US style="FONT-SIZE: 12pt"><O:P> 
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            align=center><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.1<SPAN 
            style="mso-spacerun: yes">&nbsp; </SPAN></SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">扩频系统抗宽带干扰能力示意图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><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'">对于脉冲干扰，带宽将被展宽到</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">B</SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，而有用信号恢复</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'">压缩</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'">后，保证高于干扰，见图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.2</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。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><SPAN 
            style="mso-spacerun: yes">&nbsp;&nbsp;</SPAN></SPAN></P>
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            <P class=MsoNormal 
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            align=center><IMG height=162 src="s03.files/t6.gif" width=500 
            border=0><SPAN lang=EN-US style="FONT-SIZE: 12pt">&nbsp;<O:P> 
            </O:P></SPAN></P>
            <P class=MsoNormal 
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            align=center><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">3.2<SPAN 
            style="mso-spacerun: yes">&nbsp; </SPAN></SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">扩频系统抗脉冲干扰能力示意图</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></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'">由于扩频系统这一优良性能，误码率很低，正常条件下可低到</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">l 0<SUP>-10</SUP>, </SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">最差条件下约</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt">10<SUP>-6</SUP></SPAN><SPAN 
            style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，完全能满足国内相关系统对通道传输质量的要求。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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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">&nbsp;<O:P> </O:P></SPAN></P>
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            style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; LINE-HEIGHT: 150%"><FONT 
            size=4><A name="3.3  隐蔽性好，对各种窄带通信系统的干扰很小"><FONT 
            color=#800080><B><SPAN lang=EN-US>3.3<SPAN 
            style="mso-spacerun: yes">&nbsp; </SPAN></SPAN><SPAN 
            style="FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">隐蔽性好，对各种窄带通信系统的干扰很小</SPAN></B></FONT></A></FONT><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%; 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'">由于扩频信号在相对较宽的频带上被扩展了，单位频带内的功率很小，信号湮没在噪声里，一般不容易被发现，而想进一步检测信号的参数</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'">如伪随机编码序列</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'">就更加困难，因此说其隐蔽性好。</SPAN></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'">再者，由于扩频信号具有很低的功率谱密度，它对目前使用的各种窄带通信系统的干扰很小。</SPAN><SPAN 
            lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
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            lang=EN-US style="FONT-SIZE: 12pt">&nbsp;<O:P> </O:P></SPAN></P>
            <P class=MsoNormal 
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            size=4><A name="3.4  可以实现码分多址"><FONT color=#800080><B><SPAN 
            lang=EN-US>3.4<SPAN style="mso-spacerun: yes">&nbsp; 
            </SPAN></SPAN><SPAN 
            style="FONT-FAMILY: 宋体; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">可以实现码分多址</SPAN><SPAN 
            lang=EN-US><SPAN style="mso-spacerun: yes">&nbsp; 
            </SPAN></SPAN></B></FONT></A></FONT><SPAN lang=EN-US 
            style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></P>
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