Brush up on filters

Filters find widespread use in data-acquisition systems because they remove frequencies that can alias into your measurements. A design guide from Frequency Devices can refresh your memory on filter theory and on how to choose a filter. From the guide, you'll learn how to calculate the responses of the most popular filter types: Butterworth, Bessel, Chebychev, and Cauer. Through Bode and S-plane plots, the guide shows you the responses of each filter type. Transfer functions show you how to calculate a filter's poles and zeros.

Elliptic and Chebychev filters roll off more sharply than butterworth filters, but they show ripple in the stop band.

The guide also discusses how digital filters can separate wanted signals from unwanted signals. It doesn't, however, show you examples of how to design analog and digital filters. You'll need a textbook or a more extensive design guide for that.

To download a copy in PDF format or to view the guide in HTML format, visit www.freqdev.com/guide.