2. 计算机
  3. Although a given waveform may contain frequencies over a very broad range．as a practical matter any transmission system will be

Although a given waveform may contain frequencies over a very broad range．as a practical matter any transmission system will be

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问题 Although a given waveform may contain frequencies over a very broad range．as a practical matter any transmission system will be able to accommodate only a limited band of(71)．This，in turn，limits the data rate that can be carried on the transmission  (72)．A square wave has an infinite number of frequency components and hence an infinite  (73)．However，the peak amplitude of the kth frequency component，kf，is only 1／k，so most of the  (74)in this waveform is in the first few frequency components．In general，any digital waveform will have(75)bandwidth．If we attempt to transmit this waveform as a signal over any medium，the transmission system will limit the bandwidth that can be transmitted.(2010年上半年试题)
(75)
选项 A、small
B、1imited
C、infinite
D、finite
答案C
解析 译文：虽然一个给定的波形包含了很宽的频率范围，但任何实际的传输系统只能通过有限的频率。这样，就限制了传输介质可以承载的数据速率。一个方波包含了无限多的频率成分，因而也具有无限的带宽。然而，第k个频率成分的峰值幅度kf只是1／k，所以波形的大部分能量只是包含在前面的少数频率成分中。一般来说，任何数字波形都有无限带宽。如果我们试图在某种介质上传输这种波形信号，则传输系统实际上会限制可以发送的带宽。
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