求:f(t) 的傅立叶变换 /(t) -t -92 f(t)=[u(t+)-u(t-)】+[u(t+t)-u(t-T)】 F(@)=t[Sa (ot /2)+2Sa (or ) 44 求: f (t) 的傅立叶变换 2 2 f (t) 1 2 t 2 2 f t u t u t u t u t ( ) [ ( ) ( )] [ ( ) ( )] F ( ) [ Sa ( / 2 ) 2 Sa ( )] 2