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124 Chapter 4 Digital Filters
Figure 4.6 Transposed, direct form FIR structure, N = 60
In this case the number of arithmetic operations remains the same, but the
signal level increases from left to right as more and more signal values are added.
4.3.3 Linear-Phase Structure
A major reason why FIR niters are used in practice is that they can produce an
exact linear-phase response. Linear-phase implies that the impulse response is
either symmetric or antisymmetric. An advantage of linear-phase FIR niters is
that the number of multiplications can be reduced by exploiting the symmetry (or
antisymmetry) in the impulse response, as illustrated in Figure 4.7.
Figure 4.7 Direct form linear-phase FIR structure, N = 60
The structure depicts the difference equation
