We discuss the quasienergy-band structure for a periodically driven system with translational symmetry. The parameter is so fixed that a bounded fully developed chaotic region is surrounded by regular orbits. Due to the periodicity both in space and in time, eigenvalues of the Floquet operator (quasienergies) form band structures. Its two distinct dispersion relations make it possible to divide each of the bands into chaotic and regular parts. Transitions between the two parts occur at the points of avoided crossings. Some regular parts are combined into a regular band with a diabatic transformation from the quasienergy basis to a coupled basis in which the avoided crossings are approximately replaced by real crossings. After the regular bands are removed, the nearest-neighbor-spacing statistics of the remaining bands are fitted by the Brody distribution.

• Received 16 March 1994

DOI:https://doi.org/10.1103/PhysRevE.50.910