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试题名称:通信原理一、填空或按要求简要回答问题:1.功率谱密度为 S_X(f)的平稳随机过程 X(t)经过传递函数为 H(f)的线性网络后(图1),其输出为 Y(t),则 Y(t)的功率谱密度 S_Y(f)=__,若Y(t)的平均值为 m_y,方差为σ_y~2,则 Y(t)的自相关函数R_Y(τ)在τ=0时为 R_y(0)=__。2.若 g(t)与 G(f)是一对傅里叶变换,用公式写出 g(t)的希尔伯特变换(?)(t)的傅里叶变换(?)(f)与G(f)的关系:(?)(f)=__。3.若狄拉克周期脉冲列δ_T_0(t)的解析式为:δ_T_0(t)=sum from (?) to ∞δ(t-nT_0)式中 T_0为脉冲的重复周期,那么,δ_T_0(t)的傅里叶变换δ_T_0(f)=__。4.用时域表达式为 m(t)的基带信号去调制频率为 f_c 的正弦波 Acos(2πf_(?)t):(1)DSBSC(抑制载波双边带调制)波的时域表
Title: Communication Principle First, fill in the blank or as required to answer a brief question: 1. Power spectral density S_X (f) of the stationary random process X (t) after the transfer function of H (f) of the linear network (Figure 1) If the output of Y (t) is Y (t), the power spectral density of Y (t) S_Y (f) = __, if the average value of Y (t) is m_y and the variance is σ_y ~ 2, then the autocorrelation function of Y R_Y (τ) is R_y (0) = __ when τ = 0. 2. If g (t) and G (f) are a pair of Fourier transforms, formulate the Fourier transform (?) Of the Hilbert transform (?) (T) of g ) And G (f): (?) (F) = __. 3. If the Dirac periodic pulse train δ_T_0 (t) of the analytic formula is: δ_T_0 (t) = sum from (?) To ∞ δ (t-nT_0) Where T_0 is the pulse repetition period, then δ_T_0 (t) The Fourier transform δ_T_0 (f) = __. 4. Demodulate the sine wave Acos (2πf _ (?) T) of frequency f_c with a baseband signal of time domain expression m (t): (1) Time-domain table of DSBSC (suppressed carrier double sideband modulation)