Low-noise LC oscillator with ring configuration

Abstract

A new type of oscillators proposed in this paper, can be considered to be a kind of efforts to implement a very low noise monolithic oscillator using standard CMOS processes. Until now, an LC oscillator with external inductors has produced the best noise performance, but not monolithic. Although internal implementations of inductors, generally spiral inductors, have been studied to improve their quality factor, its performance is not good enough yet or not using standard CMOS processes. On the other hand, if we adopt ring configuration of LC oscillators with spiral inductors, we can expect that its noise characteristic will be improved much more even when spiral inductors are not qualified well, because the noise decreases as the number of stage increases. Therefore, this new oscillator, called "LC-Ring oscillator", can be used practically as a local oscillator in wireless communication applications.