Optimized Design of Pulsed Waveform Oscillators and Frequency Dividers

Abstract

A technique is presented for the optimized design of oscillators and frequency dividers based on nonlinear transmission lines (NLTLs). The oscillator design relies on a closed-loop configuration containing a high-efficiency amplifier, with the loop output matched to a short NLTL. Attention is paid to the oscillator phase noise. A simple and general-application method is presented for an accurate calculation of the phase sensitivity functions with respect to specific noise sources. The predictions obtained when considering stationary and cyclo-stationary noise-source models are compared. The influence of crucial design parameters on the oscillator efficiency, pulse amplitude, and duty cycle is analyzed, as well as their impact on the phase-noise behavior. An efficient simulation technique enables the evaluation of the injection-locking capabilities during this global optimization of the oscillator in the free-running regime. The phase-noise spectrum in injection-locked conditions is analyzed in detail, considering the influence of flicker noise. A frequency division by 2 is observed in the amplifier stage loaded by the NLTL. The origin of this division is investigated, as well as the influence of the number of cells on the pulsed waveform and the division bandwidth. The techniques have been successfully applied to the design of a pulsed oscillator at 900 MHz.