噪声概率密度函数一空间独立的噪声 指数噪声 p2) P() 1 0.607、6 个 p(=g z≥0 V2ro Gaussian Rayleigh Erlang(Gamma) z<0 0.607 V2ro K= a(b-1)- e- (b-1)1 +00 E(Z)= zp(z)dz (b-1)/a + -00 p(z) P() p(z) +0∞ D(z)= (z-)2p(z)dz 1-(P+P) b-a -00 Exponential Uniform Salt-and. pepper P 02= 1 abe a a de f FIGURE 5.2 Some important probability density functions.18 噪声概率密度函数—空间独立的噪声 指数噪声 1 z = a 2 2 1 = a  𝐸(𝑧) = න −∞ +∞ 𝑧𝑝 𝑧 𝑑𝑧 𝐷 𝑧 = න −∞ +∞ 𝑧 − 𝑧ҧ 2𝑝 𝑧 𝑑𝑧 𝑝(𝑧) = ቊ 𝑎𝑒 −𝑎𝑧 𝑧 ≥ 0 0 𝑧 < 0