问题
问答题 简答题
简述频分多址的原理和特点。
答案
参考答案：
FDMA是使用较早也是现在使用较多的一种多址接入方式，它广泛应用在卫星通信、移动通信、一点多址微波通信系统中。它把传输频带划分为若干个较窄的且互不重叠的子频带，每个用户分配到一个固定子频带，按频带区分用户。信号调制到该子频带内，各用户信号同时传送，接收时分别按频带提取，从而实现多址通信。
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简述频分多址的原理和特点。
参考答案：
FDMA是使用较早也是现在使用较多的一种多址接入方式，它广泛应用在卫星通信、移动通信、一点多址微波通信系统中。它把传输频带划分为若干个较窄的且互不重叠的子频带，每个用户分配到一个固定子频带，按频带区分用户。信号调制到该子频带内，各用户信号同时传送，接收时分别按频带提取，从而实现多址通信。
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| I recently heard a story about a famous research scientist who had made several very important medical breakthroughs. What set him so far apart from others? He 1 that, in his opinion, it all came from an 2 from his mother that happened when he was about 2 years old. He had been trying to 3 a bottle of milk from the refrigerator when he lost his 4 on the slippery bottle and it 5 , making its contents pouring all over the kitchen floor. When his mother came into the kitchen, instead of 6 at him, giving him a lecture, or punishing him, she said: "Robert, what a 7 and wonderful mess you have made! I have 8 seen such a huge pool of milk. Well, the damage has already been done. Would you like to 9 down and play in the milk for a few minutes 10 we clean it up?" Indeed, he did. After a few minutes, his mother said: "You know, Robert, 11 you make a mess like this, you have to clean it up at last and 12 everything to its proper order. So, how would you like to do that? We could use a sponge (海绵), a towel, or a mop. Which do you 13 ?" He chose the sponge and together they 14 the milk. His mother then said: "You know, what happened just now is a 15 experiment in how effectively to carry a big milk bottle with two 16 hands. Let's go out in the backyard and fill the bottle with water and see if you can 17 a way to carry it without dropping it." The little boy 18 that if he held the bottle at the top near the lip with both hands, he could carry it without dropping it. This scientist then 19 that it was at that moment that he knew he didn't need to be afraid to make 20 .Wouldn't it be great if all parents would respond the way Robert's mother responded to him? | ||||
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