Finite Impulse Response Filter Design - Digital Signal Processing: Fundamentals and Applications - page 285

0

-50

-100

0 500 1000 1500 2000 2500 3000 3500 4000

Frequency (Hz)

0

-500

-1000

-1500

-2000

0 500 1000 1500 2000 2500 3000 3500 4000

Frequency (Hz)

FIGURE 7.42B

Frequency responses. The solid line indicates the FIR filter with infinite precision; the dashed line indicates the
FIR filter with the round-off coefficients.

In practical situations, a similar procedure can be used to analyze the effects of filter coefficient
quantization to make sure that the designed filter meets the requirements.

7.9 SUMMARY OF FIR DESIGN PROCEDURES AND SELECTION OF FIR
FILTER DESIGN METHODS IN PRACTICE
In this section, we first summarize the design procedures of the window design, frequency sampling
design, and optimal design methods, and then discuss the selection of the particular filter for typical
applications.
The window method (Fourier transform design using windows):

1. Given the filter frequency specifications, determine the filter order (odd number used in this topic)
and the cutoff frequency/frequencies using Table 7.7 and Equation (7.26) .
2. Compute the impulse sequence hðnÞ via the Fourier transform method using the appropriate
equations (in Table 7.1 ) .
3. Multiply the generated FIR filter coefficients hðnÞ in step 2 by the selected window sequence using
Equation (7.20) to obtain the windowed impulse sequence h w ðnÞ .