●● 3.Gaussian White Noise through Ideal Integrator ●●● ●●●● 高斯白噪声通过理想的积分器 ●●●● ●●●● H(@)=-(1-e-io) T is integral time积分时间 ●●●色 N-小rUf-5 Components:detector,demodulator 器件；检波器，解调器 The output noise power is proportional to the integration interval time.输出噪声功率与积分时间成正比 4.Mixing of Noise Function:frequency conversion N E[n2(t)cos2(@t+0)]= 2 功能：频率变换 2:average noise power or variance of input port 输入端口的平均噪声功率或方差 Conclusion: Mixing reduces the average noise power by half,due to the ensemble average of the cos@t over the range of random phase.混频把平均噪声功率减小了一半，这是由于在整个随机相位 范围内的平均
3. Gaussian White Noise through Ideal Integrator 高斯白噪声通过理想的积分器 T is integral time积分时间 Components: detector, demodulator 器件：检波器，解调器 4. Mixing of Noise Function: frequency conversion 功能：频率变换 σ 2: average noise power or variance of input port 输入端口的平均噪声功率或方差 Conclusion: Mixing reduces the average noise power by half, due to the ensemble average of the over the range of random phase.混频把平均噪声功率减小了一半,这是由于在整个随机相位 范围内的平均 2 0 cos t The output noise power is proportional to the integration interval time.输出噪声功率与积分时间成正比 17 1 ( ) (1 ) j T H e j 2 0 0 ( ) 2 2 o n T N H f df n 2 2 2 0 [ ( )cos ( )] 2 N En t t o
●●● 5.Narrowband Representation of Noise ●●●● ●●●●心 ●●●● 噪声的窄带表示 ●●●● ●●●● ●●●● It is useful in analyzing the effect of noise on the demodulation of signals..在分析噪声对信号解调的影响时有用 n(t)=x(t)cos@t+y(t)sin@t △0<<00 is the center frequency of bandpass filter, 带通滤波器的中心频率 △o is the bandwidth. y(t)sin wof n(） n,forlo<△3 s,o)=S,o)= 0 for>△3 x(r)cos wpt 18
is the center frequency of bandpass filter, 5. Narrowband Representation of Noise 噪声的窄带表示 It is useful in analyzing the effect of noise on the demodulation of signals.在分析噪声对信号解调的影响时有用 0 0 is the bandwidth. 18 ( ) ( )cos ( )sin o o nt xt t y t t 0 2 () () 0 2 x y n for S S for 带通滤波器的中心频率
●●● ●●●● ●●● §3.4 Basic Threshold Detection基本的门限检测 ●●● ●●●● ●●●● ●●●● The received signal:r(t)=s(t)+n(t) n(t):noise voltagel噪声电压 v。for transmitted"1" s0:signal voage信号电压ands0=0 or tansied"0” 个s(t) r(t)> 0ut“1” 2 → r)< 0ut“0” 2 19
§3.4 Basic Threshold Detection基本的门限检测 The received signal: n(t): noise voltage噪声电压 and "1" ( ) 0 "0" o v for transmitted s t for transmitted + 0 ( ) 2 T v r t out “1” 0 ( ) 2 T v r t out “0” Tt s(t): signal voltage信号电压 19 rt st nt () () ()