Numerical investigation of turn-on conditions in TRAPATT oscillators

A computer simulation of TRAPATT diode-circuit interactions has been used to study high-frequency oscillatory phenomena that are seen experimentally to occur simultaneously with TRAPATT initiation. The simulation combines a solution of the diode internal dynamics using the method of characteristics with a time-domain coaxial-circuit analysis. By determining its dependence on circuit and diode bias conditions, the high-frequency oscillation is shown to be a relaxation, not an IMPATT oscillation. The relaxation oscillation can be tuned by adjusting to TRAPATT bias current to minimize TRAPATT start-up time. A two-step (high-low) bias pulse, or ingenious utilization of ringing in the bias circuit, can also be used to minimize start-up time.