Splat,
Probably the best known purveyor of signal processing
applications to trading, at least for futures, is John Ehlers.
His recent book, "Rocket Science for Traders - Digital
Signal Processing for Traders" makes for interesting
reading. It's quite challenging if you don't have the
math background. He also has a book on MESA, with
a new edition to be out soon.
By the way, Ehlers' trading systems consistently appear
in the top ten rated systems of Futures Truth.
Richard