7.2.2 impulse Response of Ideal Filters o By setting all impulse response coefficients outside the range -M<=n<=M equal to zero, we arrive at a finite-length noncausal approximation of length 2M+1, which when shifted to the right yields the coefficients of a causal FiR lowpass filter sin(o(n-M) 0≤n≤N-1 h 丌(n-M 0 otherwise7.2.2 impulse Response of Ideal Filters  By setting all impulse response coefficients outside the range –M<=n<=M equal to zero, we arrive at a finite-length noncausal approximation of length 2M+1, which when shifted to the right yields the coefficients of a causal FIR lowpass filter:   ( ( )) ( ) sin , 0 1 ˆ 0, c LP n M n N h n n M otherwise    −    − =  −  