题目内容
(请给出正确答案)
[单选题]
Lucy and Lily _____the piano now.()
A.is play
B.are playing
C.play
D.Plays
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A.is play
B.are playing
C.play
D.Plays
A.This is Lily
B.I am Lily
C.Lily here, at your service
D.I am Lily from the Front Office
A . △t≤T*/3
B . △t≤T*/2
C . △t≤T*
D . △t≥T*
A.两个周期信号x(t),y(t)的和x(t)+y(t)一定是周期信号
B.两个周期信号x(t),y(t)的周期分别为2和,则其和信号x(t)+y(t)是周期信号
C.两个周期信号x(t),y(t)的周期分别为2和,其和信号x(t)+y(t)是周期信号
D.两个周期信号x(t),y(t)的周期分别为2和3,其和信号x(t)+y(t)是周期信号
ned.
A) can’t have been B) mustn’t have been
C) shouldn’t have been D) wouldn’t have been
当uS(t)为下列情况时,求题7-37图所示电路的响应uC:
(1)uS(t)=10Ɛ(t)V;
(2)uS(t)=10δ(t)V。
x1(t)的匹配滤波器,求:
(1)分别画出M0和M1的冲激响应h0(t)和h1(t)的波形;
(2)分别粗略画出M0对x0(t)和x1(t)的响应波形以及M1对x0(t)和x1(t)的响应波形;
(3)比较这些响应在t=4时的值,若保持x1(t)不变,如何修改x0(t)使接收机更容易区分x0(t)和x1(t),也即使M0对x1(t)的响应和M1对x0(t)的响应在t=4时为零值.