问题
问答题 简答题
为什么要对调频信号进行予加重?
答案
参考答案:因为通过实践可知:语言信号的能量,大部分集中在低音频段,高音频段的振幅很小,在调频时产生频移小,因此它与噪声产生的频移相对的信噪比下降,为了人为地提高归射机音频调制信号的高频分量的振幅,相对地改善信噪比,但在接收机中要加入相反作用的网络(即去加重电路)使高音频分量减弱,恢复原来的频响特性。
为什么要对调频信号进行予加重?
参考答案:因为通过实践可知:语言信号的能量,大部分集中在低音频段,高音频段的振幅很小,在调频时产生频移小,因此它与噪声产生的频移相对的信噪比下降,为了人为地提高归射机音频调制信号的高频分量的振幅,相对地改善信噪比,但在接收机中要加入相反作用的网络(即去加重电路)使高音频分量减弱,恢复原来的频响特性。
从方框中选择恰当的短语并用其正确的形式填空:
小题1: ______________________ a new shopping mall near my school.小题2: He had remembered lots of facts but couldn’t organize _________ in a good order. 小题3: Do you know how many _________ you have made this week?小题4: Are you free this afternoon? I want you ___________________ with me. 小题5: A Virgo is practical and always ______________________ details. 小题6: Milk __________________________ your health. So you must drink some every day. 小题7: It’s easy for you ________________________ if you don’t sleep well. 小题8: The boy told himself to stay awake to watch Li Na play tennis, but he fell _______ quickly.[小题9: ---- How can I be a top student? ---- You need to spend ____________________ two hours on your work after school. 小题10: Tom used to be a _____________ boy, didn’t she?小题11: I have spent much time __________ that thing to them, I’m tired .小题12: Although John is good at Maths, he never _____________.小题13: I can’t see ___________ in the teachers’ office. Where are they?小题14: I’m sorry that I was _______________ with you about the matter.小题15: There are many ____________ between Beijing and Shanghai. |