Digital Signal Processing Reference
In-Depth Information
Audio
Speaker
TMS320C6711
DSK
(programmable
as lp, hp, bp and
bs filters)
AM/FM
radio
receiver
+
HP 35665
Dynamic
Signal
Analyzer
FIGURE 8.5
Experimental setup for study of filtering effects on speech and music signals.
used to implement the different types of filtering (low-pass, high-pass, band-
pass, and bandstop). However, one new concept will be the use of the .
gel
file, or
slider
file, which will enable us to step through the four different
types of FIR filters. However, before the actual hardware testing, there are
important design steps, which are explained below.
Step 1: Design of four filter types using MATLAB
The filter design procedure for this experiment is very similar to the previous
two experiments, described in Section 8.2 and Section 8.3 However, we need
to simultaneously design four kinds of filters, using the following MATLAB
commands, and store the coefficients in their respective
*.cof
files.
•
Low-pass filter
Design a digital
low-pass
filter, having a cutoff frequency of 1.5 kHz,
using the program below.
% MATLAB Program to Calculate the FIR Low-Pass Filter
Coefficients
N = 50 ; specifies the filter order (50)
fs = 8000 ; specifies the sampling frequency (8 KHz)
f= 1500 ; specifies the analog filter cutoff
frequency in Hz.
wn = 2*pi*f/fs ; transforms the analog cutoff frequency,
f
Hz, to digital cutoff frequency,
w
n
,
rad.
wn = wn/pi ; normalizes the digital cutoff frequency
vector
h = fir1(N,wn) ; calculates the FIR low-pass filter
coefficients
