一、基带信号的频谱特性 研究基带信号的频谱结构是十分必要的,通过谱分析,我们可以了解信号需 要占据的频带宽度,所包含的频谱分量,有无直流分量,有无定时分量等。 设二进制的随机脉冲序列如图5-4(a)所示,其中1(t)表示“0”码,g2(t) 表示“1”码,g1(t)和g2(t)在实际中可以是任意的脉冲

a)PCM信号的码元速率和带宽 (1)码元速率。设m(t)最高频率为fn,f3≥fn,如果量化电平数为M, 则采用二进制代码的码元速率为 f,=f,-log2 M=f,N (6.3-27) (2)传输PCM信号所需的最小带宽。抽样速率的最小值f=2fn,这时码 元传输速率为fb=2fnN,在无码间串扰和采用理想低通传输特性的情况下

一、二进制移频键控(2FSK)系统的抗噪声性能 a)同步检测法的系统性能 带通 滤波器相乘器低通

设在基带系统接收滤波器与判决电路之间插入一个具有2N+1个抽头的横向 滤波器,如图5-21(a所示。它的输入为x(t),并设它不附加噪声

总波函数(=2S2) 若忽略耦合,则 y(s,2)=y()x(s,2)(总的Hilbert空间是位形空间和自旋空间的直积) 体系总波函数交换反对称性要求: a)空间对称y+(),自旋反对称x(S,S2), 或b)空间反对称y(,),自旋对称x(S12,S2)。 若忽略SS2耦合,自旋波函数:

一、维生素概述 二、维生素B1与羧化辅酶 三、维生素B2与黄素辅酶 四、泛酸和辅酶A 五、维生素PP和辅酶〡、辅酶Ⅱ 六、维生素B和磷酸吡哆醛 七、生物素 八、叶酸和叶酸辅酶 九、维生素B12和B12辅酶

一、(12分)已知某连续时间信号x(t)的波形如图所示。 1.画出信号x1(t)=x(2-2t)+x(t-1)的波形;x( 2.若x(t)的频谱是X(),试用X(a)表示信号x(t)的频谱

PARTO- PRELUDE: REVIEW OF UNIFIED ENGINEERING THERMODYNAMICS [AW pp 2-22, 32-41(see IAW for detailed SB&vw references): VN Chapter 1] 0.1 What it's all about The focus of thermodynamics in 16.050 is on the production of work, often in the form of kinetic energy(for example in the exhaust of a jet engine)or shaft power

The lowpass filter H(u) has a cutoff frequency wc=205T rad/ sec. Thus, c(t)is r(t) where all terms with frequency above we are removed by the lowpass filter. The terms which are kept have kwol 205T rad /sec k|< 10.25, so the output, ac(t),is r(t)= To obtain n, we sample c(t) every T=5 10-3 seconds with an impulse train The sampling frequency is 400T=2 x maximum frequency in c(t). Therefore

Department of Electrical Engineering and Computer Science 6.003: Signals and Systems-Fall 2003 Thursday, November 13. 2003 Directions: The exam consists of 5 problems on pages 2 to 19 and additional work space on pages 20 and 21. Please make sure you have all the pages. Tables of Fourier series properties as well as CT Fourier transform and DT Fourier transform properties and pairs are supplied to you as a separate set of pages. Enter all your work and