Mutual synchronization of rotary pulses in coupled tunnel-diode oscillator lattice loops

Coupled tunnel-diode oscillator lattice loops are investigated to characterize the mutual synchronization of nonlinear rotary pulses. In a properly biased lattice loop, a pulsed phase wave autonomously rotates. When two loops are coupled, these pulses are supposed to be mutually synchronized to start rotating with a fixed phase difference. To quantify the synchronization properties of both the in-phase and out-of-phase rotary pulses, two five-cell loops that are point-coupled by a capacitor are studied using bifurcation analyses with respect to the bias voltage and coupling capacitance. In-phase pulses are allowed irrespective of the coupling capacitance, whereas relatively small coupling is favorable for out-of-phase pulses. Moreover, a solution exists whose phase difference continuously varies with the bias voltage, which bifurcates from the out-of-phase pulses through pitchfork bifurcation. This study presents the result from the bifurcation analyses. For validation of the rotary pulse in the coupled loops, we measured a breadboarded test circuit in both the frequency and time domains. The in-phase, out-of-phase, and symmetry-broken rotary pulses were detected successfully.