ELEC 240 Lab

Introduction

Voltages in a circuit (so called analog signals) are continuous whereas the sequence of numbers in the computer with which we are representing it is discrete, both in time and in value. In other words, by sampling the analog signal at regular intervals we ignore any changes that may take place between these sampling times, and by representing the value by a number with a limited number of digits we introduce an error between the actual value and its representation. In the first part of this lab we will observe sampling effects using Labview.

Next, we will look at how we might use the computer alongside (or instead of) op amps as part of an overall signal processing system. We will look at some processing functions (e.g. filtering) which are direct "analogs" of analog processing, as well as some that would be difficult or impossible to implement in an analog circuit. For this, we will use Matlab to do most of our signal processing.

Matlab has a more conventional programming language, and it allows us to circumvent the real time constraint by using "batch" processing: we record a signal on disk, process it (taking as long as we need), write the resulting output to disk, and then play back the output signal. This has the additional advantage of allowing us to perform different processing functions on exactly the same input (reference) signal and compare the results.

We will also look a bit further into the process of filter design and implementation. Then we will try generating signals digitally, as well as filtering them. Finally, we'll look at some applications that are more elaborate than simply filtering signals.