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FIR Filter Structures 231
FIGURE 6.12
Linear-phase form FIR structures (symmetric impulse response)
□ EXAMPLE 6.4 An FIR filter is given by the system function
H(z) =1+16 1
16 z−4 + z −8
Determine and draw the direct, linear-phase, and cascade form structures.
a. Direct form: The difference equation is given by
y(n) =x(n)+16.0625x(n − 4) + x(n − 8)
and the direct form structure is shown in Figure 6.13(a).
b. Linear-phase form: The difference equation can be written in the form
y(n) =[x(n)+x(n − 8)]+16.0625x(n − 4)
and the resulting structure is shown in Figure 6.13b.
c. Cascade form: We use the following MATLAB Script.
>> b=[1,0,0,0,16+1/16,0,0,0,1]; [b0,B,A] = dir2cas(b,1)
FIGURE 6.13 FIR filter structures in Example 6.4
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