Low Power Low Phase Noise Stacked Quadrature Ring Oscillator

D. Novais, J. Santa-Rita, L. Oliveira, J. Oliveira (NOVA School of Science and Techn., Portugal), J. Casaleiro (Inst. Superior de Engenharia de Lisboa, Portugal)

Traditional ring oscillators are usually designed to have an odd number of inverter stages, however modern communication systems use quadrature signals, which cannot be directly produced by a single-ended odd-numbered ring oscillator. Development of single-ended even-numbered ring oscillators is therefore necessary to directly produce quadrature output. This paper aims to improve the performance of an already existing QRO (Quadrature Ring Oscillator) by introducing a strong injection locking technique, achieved with stacking the oscillator’s inverters to reduce the circuit power consumption. This technique shows a phase noise improvment of 4.3 dBc/Hz (@ 10MHz) while at the same time consuming less than half the power of a Classic QRO topology.