Subharmonically injection-locked oscillator using a nonlinear transmission line

This work describes a first realization of an oscillator driven through a nonlinear transmission line (NLTL). In this way, the oscillator is able to synchronize to a sinusoidal injection source of much lower frequency. This can be understood as the result of two processes: high harmonic generation in the NLTL and frequency multiplication plus mixing in the oscillator device. The concept can be applicable in ultrawideband signal oscillators where synchronization should enable a fast oscillation start-up and facilitate the modulation process. As an example, it has been used here to obtain a pulsed-envelope oscillator at 6 GHz injected with a sinusoidal signal in the order of 100 MHz. The operation bands have been analyzed with a Poincaré map technique, allowing the detection of the bifurcation phenomena that delimit the stable synchronization ranges. For an understanding of the phase-noise spectrum, this spectrum is analyzed at higher injection frequencies with the conversion matrix approach. Very good results have been obtained in comparison with measurements.