Page 369 - Analog and Digital Filter Design

366 Analog and Digital Filter Design

Consider a simple filter, comprised of a two-input adder and a single delay
element with a multiplier. Let the multiplier coefficient be -0.5. Table 15.1 shows
how the filter responds.

SAMPLE I INPUTA OUTPUTA INPUT B OUTPUT B

0 0 -0.37 0 -0.3
1 0.3 1292 0.12792 0.95600 0.80600
2 0.59441 0.65837 0.56087 0.96388
3 0.81620 1.14538 -0.6269 -0.1450
4 0.95600 1.52870 -0.9287 -1.0012
5 0.99978 1.76414 0.08209 -0.4185
6 0.943 14 1.82521 0.97686 0.76760
7 0.79177 1.70438 0.49101 0.87482
8 0.56087 1.41306 -0.6887 -0.25 13
9 0.27 3 64 0.98017 -0.8951 -1.0208
10 -0.0410 0.44900 0.16363 -0.3467
11 -0.3516 -0.1271 0.99 1 12 0.8 1773
12 -0.6269 -0.6905 0.41784 0.8267
13 -0.8392 -1.1845 -0.7459 -0.3326
14 -0.9672 -1.5595 -0.8555 -1.0218
15 -0.998 1 -1.7778 0.24407 -0.2668
16 -0.9287 -1.8176 0.99869 0.86527

Table 15.1
The Response of an IIR Filter

The response for a sinusoidal signal with an angular change of l/z radians per
sample is given by output A. The response of a sinusoidal signal having an
angular change of 4/z radians per sample is given by output B.

DSP Mathematics

Digital signal processing will dominate over analog techniques with the intro-
duction of low-cost DSP chips and kits. Kits are already available at low cost.
These have a processor board with input and output interfaces, and assembler
and debugger software that enable code to be tested. Texas Instruments pro-
duces a kit called the DSK, which contains a TMS320C50 DSP device and an
analog interface circuit. Analog Devices produces the EZ-KIT, which contains
the AD2101 DSP and the EZ-KIT Lite, which contains the AD21 15. Motorola
has also joined in the low-cost introduction market with the DSP56002EVM,
this contains a DSP56L002, which is a 24-bit fixed-point processor.