Digital Signal Processing Reference
In-Depth Information
/*
FIR3LP.gel
Gel file to step through three different LP filters*/
menuitem "Filter Characteristics"
slider Filter(0,2,1,1,filterparameter) /*from 0 to 2,incr by 1*/
{
LP_number = filterparameter; /*for 3 LP filters*/
}
FIGURE 4.14.
GEL file for selecting one of three FIR lowpass filter coefficients
(
FIR3LP.gel
).
FIGURE 4.15.
Frequency response of a FIR lowpass filter with a bandwidth of 3000 Hz using
LP3000.cof
, obtained with a signal analyzer.
the lower bandwidth of 600 Hz, using the first set of coefficients, the frequency com-
ponents of the speech signal above 600 Hz are suppressed. Connect the output to a
speaker or a spectrum analyzer to verify such results, and observe the different
bandwidths of the three FIR lowpass filters. The shareware utility Goldwave gen-
erates different signals, including noise, using a sound card (see Appendix E). The
output from the sound card with the noise generated by Goldwave can be used as
the input to the DSK. Connecting the output from the DSK as the input to the
sound card, Goldwave can also be used as a virtual spectrum analyzer. The fre-
quency responses of these three lowpass filters can be obtained readily in real time.
Figure 4.15 shows the frequency response of the 3000-Hz lowpass FIR filter,
obtained with an HP signal analyzer.
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