Region1:r≤a无源区域 C B.2元r= 0..B,=0..B=0 Region2:a≤r≤b有源区域 B26 2Tr=Aol2p-lo.S=Ao a丌(r 丌(b2-a B ,b=aB 2zr((b2-a2) 2mr(b2-a2) Region3:b≤r无源区域 B42兀r= ∵.B B=aB 27 2IrRegion 1 :ra 无源区域 1 0 1 1 1 B r I B B 2 0 0 0 = 内 = = = Region 3: b r 无源区域 Region2: a r b 有源区域 ( ) ( ) ( ) 2 2 2 0 0 0 2 2 2 2 2 2 2 0 0 2 2 2 2 2 ˆ ˆ ( ) ˆ ˆ 2 ( ) 2 ( ) z z I B r I J S a r a a b a I r a r a I B B a B a r b a r b a = = − = = = − − 内 = - - - b r a b a r 0 0 0 2 ˆ ˆ 2 2 B r I I I B B a B a r r = = = = b r a