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ANALOG FILTERR fC fX(tlbX(t)INPUTFROMSENSORy(t)OUTPUT Y(ll~TOACTUATORty(t) Rf[ 1 -lXTt) = -R; 1 + jwRF tJFREQUENCY CHARACTERISTICSIDEALFILTERFREQUENCYFigure 1-1 Analog Signal ProcessingThe equivalent circuit using a DSP is shown in Figure 1-2. This application requires ananalog-to-digital (AID) converter and digital-to-analog (DI A) converter in addition to theDSP. Even with these additional parts, the component count can be lower using a DSPdue to the high integration available with current components.Processing in this circuit begins by band-limiting the input with an anti-alias filter, eliminatingout-<strong>of</strong>-band signals that can be aliased back into the pass band due to the samplingprocess. The signal is then sampled, digitized with an AID converter, and sent to the DSP.The filter implemented by the DSP is strictly a matter <strong>of</strong> s<strong>of</strong>tware. The DSP can directlyimplement any filter that can also be implemented using analog techniques. Also, adaptivefilters can be easily implemented using DSP, whereas these filters are extremelydifficult to implement using analog techniques.The DSP output is processed by a D/A converter and is low-pass filtered to remove theeffects <strong>of</strong> digitizing. In summary, the advantages <strong>of</strong> using the DSP include the following:

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