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color=#000066>时域均衡系统的主体是横向滤波器，也称横截滤波器，它由多级抽头延迟线、加权系数相乘器（或可变增益电路）及相加器组成，如图<SPAN
lang=EN-US>3-21。<O:P> </O:P></SPAN></FONT></P>
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style="TEXT-JUSTIFY: inter-ideograph; TEXT-INDENT: 73.5pt; TEXT-ALIGN: justify; mso-char-indent-count: 7.0; mso-char-indent-size: 10.5pt"><FONT
face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>
<IMG height=152 src="g3-4-5.files/g3-3.H3.gif" width=350
v:shapes="_x0000_i1027"><O:P> </O:P></SPAN></FONT></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066>图<SPAN
lang=EN-US>3－21<SPAN style="mso-spacerun: yes">
</SPAN>横向滤波器<O:P> </O:P></SPAN></FONT></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US><O:P></O:P></SPAN></FONT></P>
<P class=MsoNormal
style="TEXT-JUSTIFY: inter-ideograph; TEXT-INDENT: 21pt; TEXT-ALIGN: justify"><FONT
face=楷体_GB2312
color=#000066>自适应均衡器所追求的目标就是要达到最佳抽头增益系数，是直接从传输的实际数字信号中根据某种算法不断调整增益，因而能适应信道的随机变化，使均衡器总是保持最佳的工作状态，有更好的失真补偿性能，自适应均衡器需有三个特点：快速初始收敛特性、好的跟踪信道时变特性和低的运算量。因此，实际使用的自适应均衡器系统除在正式工作前先发一定长度的测试脉冲序列，又称训练序列，以调整均衡器的抽头系数，使均衡器基本上趋于收敛，然后再自动改变为自适应工作方式，使均衡器维持最佳状态。自适应均衡器一般还按最小均方误差准则来构成，最小均方算法采用维特比（<SPAN
lang=EN-US>“Viterbi）算法。维特比算法其实质就是最大似然比算法，维特比均衡器的方框图如图3-22。<O:P>
</O:P></SPAN></FONT></P>
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style="TEXT-JUSTIFY: inter-ideograph; TEXT-INDENT: 63pt; TEXT-ALIGN: justify; mso-char-indent-count: 6.0; mso-char-indent-size: 10.5pt"><FONT
face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>
<IMG height=146 src="g3-4-5.files/g3-3.H4.gif" width=360
v:shapes="_x0000_i1028"><O:P> </O:P></SPAN></FONT></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066>图<SPAN
lang=EN-US>3－22<SPAN style="mso-spacerun: yes">
</SPAN>维特比均衡器<O:P> </O:P></SPAN></FONT></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US><O:P></O:P></SPAN></FONT></P>
<P class=MsoNormal
style="TEXT-JUSTIFY: inter-ideograph; TEXT-INDENT: 21pt; TEXT-ALIGN: justify"><FONT
face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>GSM数字移动通信系统中的训练序列如表3-1，它们具有很好的自相关性，以使均衡器具有很好的收敛性。<O:P>
</O:P></SPAN></FONT></P>
<P class=MsoNormal style="TEXT-INDENT: 21pt; TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066>表<SPAN
lang=EN-US>3-1<SPAN style="mso-spacerun: yes">
</SPAN>GSM系统的训练序列<O:P> </O:P></SPAN></FONT></P>
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066>序数<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></P></TD>
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align=center><FONT face=楷体_GB2312 color=#000066>十进制<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></P></TD>
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align=center><FONT face=楷体_GB2312 color=#000066>八进制<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></P></TD>
<TD
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066>十六进制<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></P></TD>
<TD
style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: windowtext 0.5pt solid; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 127.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt"
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align=center><FONT face=楷体_GB2312 color=#000066>二进制<SPAN
lang=EN-US><O:P> </O:P></SPAN></FONT></P></TD></TR>
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style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 27.35pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-top-alt: solid windowtext .5pt"
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>1<O:P> </O:P></SPAN></FONT></P></TD>
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style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 58.45pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt"
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>9898135<O:P> </O:P></SPAN></FONT></P></TD>
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>45604227<O:P> </O:P></SPAN></FONT></P></TD>
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>970897<O:P> </O:P></SPAN></FONT></P></TD>
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style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 127.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt"
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align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">00100101110000100010010111<O:P>
</O:P></SPAN></FONT></P></TD></TR>
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vAlign=top width=36>
<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>2<O:P> </O:P></SPAN></FONT></P></TD>
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style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 58.45pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt"
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>12023991<O:P> </O:P></SPAN></FONT></P></TD>
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style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 64.6pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt"
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>55674267<O:P> </O:P></SPAN></FONT></P></TD>
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US>B778B7<O:P> </O:P></SPAN></FONT></P></TD>
<TD
style="BORDER-RIGHT: windowtext 0.5pt solid; PADDING-RIGHT: 5.4pt; BORDER-TOP: medium none; PADDING-LEFT: 5.4pt; PADDING-BOTTOM: 0cm; BORDER-LEFT: medium none; WIDTH: 127.8pt; PADDING-TOP: 0cm; BORDER-BOTTOM: windowtext 0.5pt solid; mso-border-left-alt: solid windowtext .5pt; mso-border-top-alt: solid windowtext .5pt"
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<P class=MsoNormal style="TEXT-ALIGN: center"
align=center><FONT face=楷体_GB2312 color=#000066><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">00101101110111100010110111<O:P>
</O:P></SPAN></FONT></P></TD></TR>
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