Full-wave analysis of traveling pulses developed in a system of transmission lines with regularly spaced resonant-tunneling diodes

In a system of transmission lines with regularly spaced resonant-tunneling diodes (RTDs), where several straight RTD lines are connected halfway to a closed RTD line, a pulse-shaped rotary traveling wave develops on the closed line by mutual synchronization of the oscillatory edge developed in each straight RTD line. The oscillating edge on each straight line is synchronized with the traveling pulse, such that the system has the potential to generate multiphase oscillatory signals in millimeter-wave frequencies. To examine the dynamics of traveling pulses at such high frequencies, the system is modeled in the framework of the finite-difference time-domain method. It is found that a traveling pulse develops in the closed RTD line synchronized with the oscillatory edges moving in the straight lines, assuming a microstrip structure for each RTD line. We then compare the results of the finite-difference time-domain calculation with those predicted by the transmission line theory with parameter values obtained by the quasi-transverse electromagnetic estimation. In addition, the RTD line that compactly confines the electromagnetic fields is shown to have the potential to generate multiphase oscillatory signals at submillimeter-wave frequencies.