5.1.1 Ideal Frequency-Selective Filters Ideal highpass filter l-eH(e-e3e ◆Noncausal,not hmln]=8fn] sinan -o0<n<o0 computationally 元n realizable ◆no phase distortion H(e) -2元 0 2元 65.1.1 Ideal Frequency-Selective Filters ◆Ideal highpass filter     sin , c h n n hp n n n    = − −  − 2 − −c 0 c  2 ( ) H ej 1 6 ◆Noncausal, not computationally realizable ◆no phase distortion ( ) ( )  0, | | 1 1, | | j c hp c j Hlp e H e         − = =  