噪声概率密度函数一空间独立的噪声 b=1时 Erlang (Gamma)Noise p(z) P() p(z) 1 2 V2r0 0.607、 Gaussian Rayleigh Erlang(Gamma) abzb-1 0.607 p(Z)= e-az z≥a (b-1) K=a6-1)-1 b-1月e6- 0 z<a i-g ii+o b (6-1)/@ r00 +2 E(a)= zp(z)dz p(z) p() p(z) -00 1 1-(P+P) Exponential b-a +00 Uniform Salt-and- D(z)= (z-2)2p(z)dz pepper b ab e a de f FIGURE 5.2 Some important probability density functions. 17 噪声概率密度函数—空间独立的噪声 Erlang (Gamma) Noise 𝑝(𝑧) = ൞ 𝑎 𝑏 𝑧 𝑏−1 𝑏 − 1 ! 𝑒 −𝑎𝑧 𝑧 ≥ 𝑎 0 𝑧 < 𝑎 = b z a 2 2 = b a  𝐸(𝑧) = න −∞ +∞ 𝑧𝑝 𝑧 𝑑𝑧 𝐷 𝑧 = න −∞ +∞ 𝑧 − 𝑧ҧ 2𝑝 𝑧 𝑑𝑧 b=1时