Analytical model for CMOS cross-coupled LC-tank oscillator

Periodic steady-state behaviour of cross-coupled LC-tank oscillator is of critical importance in ultra-low power, low-voltage transceiver circuits. Understanding the major factors affecting amplitude, oscillation frequency and power consumption would lead to more optimised oscillator design particularly for short-range wireless transceivers. This study presents a new approach for evaluating the amplitude of the main component, oscillation frequency and power consumption of cross-coupled LC-tank oscillator. Three major factors, affecting oscillator functionality are examined. In order to obtain a general design methodology, the effects of oscillator parameters such as transistors’ sizes, inductor and capacitor values are investigated. An intuitive discussion about oscillator behaviour and a design procedure are presented. The theoretical results are verified by circuit simulations in the 0.18 µm CMOS process.