5.1.1 Ideal Frequency-Selective Filters idea owpas fiter: ◆Noncausal,not in computationally realizable ◆no phase distortion H( -2π-7π-00 2π 55.1.1 Ideal Frequency-Selective Filters ◆Ideal lowpass filter: 5 ◆Noncausal, not computationally realizable ◆no phase distortion   sin , c lp n h n n   = −    n ( )  , | | , 0, | | j 1 c lp c H e        =   ( ) j H e  − 2 − −c 0 c  2 1