We have first observed the quasiperiodicity in a single doide circuit, which has been observed only in the coupled diode systems. Most of the observations could be understood in the frame of the existing theories of the nonlinear dynamic chaos.
The wiggling in return map, another novel observation near the 1/5 lock-in frequency, could be explained by the unstable saddle-node bifurcation of the orbit on the M$\ddot{o}$bius band.
The capacitance of the diode was also measured carefully as a function of bias voltage. It shows a nonlinear anomaly characterized by negative slope and negative value in the frequency region where the quasiperiodicity appears. It seems that the quasiperiodicity may be caused by this anomaly.
