Digital Signal Processing Reference
In-Depth Information
the magnitude response similar to an FIR design, as well as a plot of the poles and
zeros of
H
(
z
), can be obtained.
E.3 FIR FILTER DESIGN USING A FILTER DEVELOPMENT PACKAGE
A noncommercial filter development package appears on the accompanying CD.
The program
FIRprog.bas
, written in BASIC, calculates the coefficients of an FIR
filter. This program is discussed in Refs. 5 to 7. It allows for the design of lowpass,
highpass, bandpass, and bandstop FIR filters using the rectangular, Hanning,
Hamming, Blackman, and Kaiser window functions. The resulting coefficients can
be generated in integer or float format. This file with the coefficients needs to be
modified and incorporated into one of the generic FIR programs.
E.3.1 Kaiser Window
1.
Run BASIC (GWBASIC) and load/run the program
FIRprog.bas.
Figures
E.3
a
and E.3
b
show a display of available window functions and the
frequency-selective filters that can be designed. Select the Kaiser window
option and a bandpass filter. A separate module for the Kaiser window
(
FIRproga.bas
) is called from
FIRprog.bas.
Main Menu
————————
1. . . .RECTANGULAR
2. . . .HANNING
3. . . .HAMMING
4. . . .BLACKMAN
5. . . .KAISER
6. . . .Exit to DOS
Enter window desired (number only) -> 5
(
a
)
Selections:
1. . . .LOWPASS
2. . . .HIGHPASS
3. . . .BANDPASS
4. . . .BANDSTOP
5. . . .Exit back to Main Menu
Enter desired filter type (number only) -> 3
(
b
)
FIGURE E.3.
FIR filter design with a filter development package (on CD): (
a
) choice of
windows; (
b
) type of filter; (
c
) filter specifications; (
d
) menu for coefficients format.
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