Jason,

Here's an idea that should actually be fun. Grab your favorite spreadsheet program and use it to actually try out the ideas that Steve and Christoph are suggesting. In just a few minutes you should have a tool that will give you a gut feel for how the numbers work out and what happens when you change the filter parameters.

If you like what you see, then you're in business. If not, you can play with your spreadsheet model until you do.

Just as an example, following is an Excel screen shot that shows the response of the filter first given by Steve to a square wave input.

-- Russ