Signal mixing in a ratchet device: commensurability and current control Sergey Savel'ev, Fabio Marchesoni, Peter Hänggi and Franco Nori Eur. Phys. J. B, 40 4 (2004) 403-408 Published online: 13 July 2004 DOI: 10.1140/epjb/e2004-00208-8