Far field expressions (r>λr>D)》 头 ao-员[xapk町 E(6,p) .dp)-ix x 2 2n Poynting vector Antenna's radiation vector source (antenna) P' Mme.p)=j.Pep[i小aW 上 j,≠0  E(r,θ,ϕ) ≈ − j η 2λ ˆ i r ×  M (θ,ϕ) × ˆ i r ⎡ ⎣ ⎤ ⎦ e− jβr r  H (r,θ,ϕ) ≈ 1 η ˆ i r ×  E  S= 1 2  E ×  H* =  E 2 2η ˆ i r  M(θ,ϕ) ≈  Ji(P') V ' ∫ exp jβ  r '⋅ˆ i ( r ) ⎡ ⎣ ⎤ ⎦dV ' Far field expressions ( r >> λ r >> D ) Antenna’ s radiation vector V’ P’ P r ’ r y x z D  Eo (θ,ϕ)   Ji ≠  0                               M t  source (antenna) Poynting vector