X(f)=1+e ,-j2m△t +e-22A +e-2730 4(2m△An) e sin[2(2n△A) j3(2m△)/2 e sn(2m△)2] X(~sm22△ sn(2m△t)/2 3(2m/△t) Sn[2(27△) 2 sn[(2m△t)/2] ∠X() 3(27f△) n[2(2mt) 十丌 0 sn[(2m△1)/2]3(2 )/ 2 2 4(2 ) 2 2 2 2 3 sin[( 2 )/ 2] sin[ 2(2 )] 1 1 ( ) 1 j f t j f t j f t j f t j f t j f t e f t f t e e X f e e e −  −  −  −  −  −    = − − = = + + +         sin[( 2 )/ 2] sin[ 2(2 )] ( ) f t f t X f   =               +  −     −  = 0 sin[ (2 )/ 2] sin[2 (2 )] , 2 3(2 ) 0 sin[ (2 )/ 2] sin[2 (2 )] , 2 3(2 ) ( ) f t f t f t f t f t f t X f        当 当