?? s03.htm
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</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">擴頻通信是唯一能夠工作于負信噪比條件下的通信方式。</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt"><O:P> </O:P></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">對于寬帶干擾和脈沖干擾在擴頻設備中如何被抑制的物理過程，可以用圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.1</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">和圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.2</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">加以說明。</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: 21.75pt; LINE-HEIGHT: 150%"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">對于各種形式人為的</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如電子對抗中</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">干擾或其他窄帶或寬帶</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">擴頻</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">系統的干擾，</SPAN><SPAN
style="FONT-SIZE: 12pt"> </SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">只要波形、時間和碼元稍有差異，解擴后仍然保持其寬帶性，而有用信號將被壓縮，見圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.1</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; 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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style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><SPAN
lang=EN-US style="FONT-SIZE: 12pt"></SPAN> </P>
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style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"
align=center><IMG height=158 src="s03.files/t5.gif" width=500
border=0><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: 21.75pt; LINE-HEIGHT: 150%; TEXT-ALIGN: center"
align=center><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.1<SPAN
style="mso-spacerun: yes"> </SPAN></SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">擴頻系統抗寬帶干擾能力示意圖</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: 21.75pt; LINE-HEIGHT: 150%"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">對于脈沖干擾，帶寬將被展寬到</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">B</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，而有用信號恢復</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">壓縮</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">后，保證高于干擾，見圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.2</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; 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"> </SPAN></SPAN></P>
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style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"> </P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"
align=center><IMG height=162 src="s03.files/t6.gif" width=500
border=0><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: 21.75pt; LINE-HEIGHT: 150%; TEXT-ALIGN: center"
align=center><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">圖</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">3.2<SPAN
style="mso-spacerun: yes"> </SPAN></SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">擴頻系統抗脈沖干擾能力示意圖</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: 21.75pt; LINE-HEIGHT: 150%"><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">由于擴頻系統這一優良性能，誤碼率很低，正常條件下可低到</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">l 0<SUP>-10</SUP>, </SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">最差條件下約</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">10<SUP>-6</SUP></SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">，完全能滿足國內相關系統對通道傳輸質量的要求。</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: 21.75pt; LINE-HEIGHT: 150%"></P>
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style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21.75pt; LINE-HEIGHT: 150%"><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: 21.75pt; LINE-HEIGHT: 150%"><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; LINE-HEIGHT: 150%"><FONT
size=4><A name="3.3 隱蔽性好，對各種窄帶通信系統的干擾很小"><FONT
color=#800080><B><SPAN lang=EN-US>3.3<SPAN
style="mso-spacerun: yes"> </SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">隱蔽性好，對各種窄帶通信系統的干擾很小</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">由于擴頻信號在相對較寬的頻帶上被擴展了，單位頻帶內的功率很小，信號湮沒在噪聲里，一般不容易被發現，而想進一步檢測信號的參數</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">(</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">如偽隨機編碼序列</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 12pt">)</SPAN><SPAN
style="FONT-SIZE: 12pt; FONT-FAMILY: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">就更加困難，因此說其隱蔽性好。</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: 宋體; mso-ascii-font-family: 'Times New Roman'; mso-hansi-font-family: 'Times New Roman'">再者，由于擴頻信號具有很低的功率譜密度，它對目前使用的各種窄帶通信系統的干擾很小。</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%; mso-char-indent-count: 2.0; mso-char-indent-size: 12.0pt"><SPAN
lang=EN-US style="FONT-SIZE: 12pt"> <O:P> </O:P></SPAN></P>
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size=4><A name="3.4 可以實現碼分多址"><FONT color=#800080><B><SPAN
lang=EN-US>3.4<SPAN style="mso-spacerun: yes">
</SPAN></SPAN><SPAN
style="FONT-FAMILY: 宋體; mso-ascii-font-family: Times New Roman; mso-hansi-font-family: Times New Roman">可以實現碼分多址</SPAN><SPAN
lang=EN-US><SPAN style="mso-spacerun: yes">
</SPAN></SPAN></B></FONT></A></FONT><SPAN lang=EN-US
style="FONT-SIZE: 12pt"><O:P></O:P></SPAN></P>
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