A filter can shift one frequency a set amount. BUT...for a anything-in, anything-out circuit, you cascade a zillion *all-pass filters* (also called a PDN: phase-differencing network). Electronotes had a good issue on the proper design of these. You need a 90 degree shift from say 20 to 20kHz: takes something like 14-16 filters in a row. This is what Bode called a "dome filter". Paul S.
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Re: [motm] phase shifting WAS: module concept
2000-04-16 by Paul Schreiber