1.2.3 Digital filters /966 Digital filters are an important class of LTI systems. Nonrecursive filter(FIR) M-1 y(m)=∑bx(n-k) k=0 Recursive filter(IIR) M-l 0m）=-2a0n-k)+2b,an-k) k=0 y(n+1)=ay(n)+bu(n) u(n) a y(n) y(n+) D 2021年2月 92021年2月 9 1.2.3 Digital filters  Digital filters are an important class of LTI systems.  Nonrecursive filter (FIR)  Recursive filter (IIR) 1 1 0 ( ) ( ) ( ) N M k k k k y n a y n k b x n k           1 0 ( ) ( ) M k k y n b x n k      y(n 1)  ay(n)  bu(n) X + D X y(n) u(n) b a y(n+1)