Design of pulsed waveform oscillators with a short nonlinear transmission line

In this paper we present a new methodology for the design of pulsed-waveform oscillators. The design is based on the use of a short section of nonlinear transmission line (NLTL), constituting the load of a transistor-based subnetwork exhibiting negative resistance. The oscillation start-up conditions are imposed at a transistor port different from the one at which the NLTL is connected, to increase the optimization flexibility. The NLTL is ended in a reactive termination which is optimized in order to reduce the duty cycle of the voltage waveform. Compared with previous works, the new methodology enables a smaller duty cycle with less varactor diodes and no need for adaptive gain in the transistor stage. The methodology has been applied to obtain a pulsed-waveform oscillator at 1.2 GHz, achieving a 5% duty cycle. Good agreement has been obtained in the comparison with the experimental results.