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<TD borderColor=#6699ff><FONT
size=2>您的位置：技术园地>技术讲座-GSM蜂窝移动通信系统 </FONT></TD></TR>
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<DIV align=center><FONT size=4><B><SPAN
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lang=EN-US>第三讲 GSM关键技术</SPAN></SPAN></B></FONT></DIV></TD></TR>
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style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><B>3.10<SPAN
style="mso-spacerun: yes"> </SPAN>跳频技术<O:P>
</O:P></B></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-ALIGN: justify"><SPAN
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style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"> </SPAN><SPAN
lang=EN-US
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
size=3><FONT face=楷体_GB2312
color=#000066>采用跳频技术是为了确保通信的秘密性和抗干扰性，它首先被用于军事通信，<BR>后来在GSM标准中也被采纳。<O:P>
</O:P></FONT><FONT face=楷体_GB2312><O:P></O:P></FONT><FONT
face=楷体_GB2312><O:P></O:P></FONT><O:P></O:P></FONT></SPAN></P>
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style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-ALIGN: justify"><SPAN
lang=EN-US
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size=3><SPAN
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</SPAN><FONT face=楷体_GB2312 color=#000066>跳频功能主要是：<O:P>
</O:P></FONT></FONT></SPAN></P>
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size=3><SPAN style="mso-hansi-font-family: Times New Roman"><SPAN
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</SPAN><FONT face=楷体_GB2312 color=#000066>(1) 改善衰落。</FONT><O:P>
</O:P></SPAN></FONT></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-ALIGN: justify"><FONT
size=3><SPAN style="mso-hansi-font-family: Times New Roman"><SPAN
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</SPAN><SPAN lang=EN-US
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066>(2)
处于多径环境中的漫速移动的移动台通过采用跳频技术，大大改善移动台的通信质量，相当于频率分集。</FONT><O:P>
</O:P></SPAN></SPAN></FONT></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-ALIGN: justify"><FONT
size=3><SPAN style="mso-hansi-font-family: Times New Roman"><SPAN
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</SPAN><FONT face=楷体_GB2312 color=#000066>(3) 跳频相当于频率分集<O:P>
</O:P></FONT></SPAN></FONT></SPAN></FONT></P>
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style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066 size=3>GSM系统中的跳频分为基带跳频和射频跳频两种。<O:P>
</O:P></FONT></SPAN></P>
<P class=MsoNormal
style="MARGIN-TOP: 0px; TEXT-JUSTIFY: inter-ideograph; MARGIN-BOTTOM: 0px; TEXT-INDENT: 21pt; TEXT-ALIGN: justify"><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066
size=3>基带跳频的原理是将话音信号随着时间的变换使用不同频率发射机发射，其原理图如图<SPAN
lang=EN-US>3-35所示，实施的方框图如图3-36所示。</SPAN></FONT><FONT size=3><SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></SPAN></P>
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size=3><SPAN lang=EN-US><O:P></O:P></SPAN></FONT></SPAN></P>
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<IMG height=113 src="g3-10.files/g3-10.1.gif" width=321
v:shapes="_x0000_i1025"><O:P> </O:P></FONT></SPAN></P>
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align=center><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066 size=3>图<SPAN lang=EN-US>3-35
基带跳频原理<O:P> </SPAN></FONT></SPAN></P>
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size=3><SPAN lang=EN-US> </SPAN></FONT></SPAN></P>
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align=center><SPAN
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size=3><SPAN lang=EN-US></SPAN></FONT></SPAN></P>
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align=center><SPAN lang=EN-US
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size=3><IMG height=127
src="g3-10.files/g3-10.2.gif" width=347
v:shapes="_x0000_i1026"><O:P> </O:P></FONT></SPAN></P>
<P class=MsoNormal
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align=center><SPAN
style="FONT-FAMILY: 宋体; mso-hansi-font-family: 'Times New Roman'"><FONT
face=楷体_GB2312 color=#000066 size=3>图<SPAN lang=EN-US>3-36
基带跳频实施框图<O:P> </O:P></SPAN></FONT></SPAN></P>
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