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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>第五讲
直接序列扩频系统(5)</FONT></SPAN></B></FONT></DIV></TD></TR>
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<P class=MsoNormal
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color=#800080><B><FONT size=4><SPAN lang=EN-US>5.5
直扩系统的性能</SPAN></FONT></B></FONT></P>
<P class=MsoNormal
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color=#000080><SPAN lang=EN-US style="FONT-SIZE: 12pt">5.5.1<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'">直扩系统的抗干扰性</SPAN></FONT><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><FONT color=#000080><SPAN
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</SPAN></FONT><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'">直扩系统最重要的应用就是在军事通信中作为一种具有很强抗干扰性的<BR>通信手段。在实际中我们遇到的干扰主要有下面几种：宽带噪声干扰、部分频带噪声干扰、单音及多音载频干扰、脉冲干扰等。图</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">5</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">20</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">是这几种干扰的频谱</SPAN><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></P>
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lang=EN-US style="FONT-SIZE: 12pt">5</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">20<O:P> </O:P></SPAN></P>
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</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">现把直扩系统对这几种干扰信号的抗干扰性简述如下：</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">图5-21</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'">对于宽带噪声，在图</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">5</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">21(a)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">示出，经过解扩中与本地</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">PN</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">相乘以后相关输出仍然是宽带噪声，且噪声功率谱密度不变。但是经窄带滤波的作用后，输出信息的信噪比，仍改善了处理增益的分贝数。故直扩系统有足够高的</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">Gp</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">时，对宽带噪声是有很好的抗干扰作用的。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><SPAN
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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'">对于部分频带噪声干扰，由于能量相对集中，对直扩系统的危害比宽带噪声要大一些。换句话说，直扩系统对其抗干扰性低于对宽带噪声的抗干扰性。</SPAN></P>
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