DFT变换 (,)=c2",1=k7/N Ne-2ik/N = 1 N-1 1(-1)2DFT变换    ( , ) , / , ... ... ... ... ... ... ... / / ( ) i t e t kT N a N e w w A w w w w j i t T ik j ik N ik N N N N = = = = = =             − − − − − 2 2 1 1 1 1 1 1 1 1 1 1 2