Studies of the dc biased Josephson junction coupled to a resonant tank

We have investigated the dynamics of a Josphson junction circuit, which con sists of a dc biased Josephson junction coupled to a resonant tank. Numeric al simulations indicate that period-3 and chaotic states coexist when this system is driven by a proper external dc current. The detailed structures o f the attractors and the basins of attraction are given to specify the feat ures of these states. This provides one with valuable information to avoid chaos in Josephson junction devices.