Last passage time models applied to phase noise of ring oscillators used in some PAN (personal area network) wireless standards

Due to the less stringent requirements of some PAN (personal area network) wireless standards such as (802.15.3, ZigBee(802.15.4)), low cost ring oscillators operating in low power are frequently applied to perform frequency synthesis in the receivers. In this paper last passage time models are applied to model the phase noise of such ring oscillators. This model leads to significant improvement in power/ phase noise trade-off. It shows that the power required is 3-4 times larger than what conventional first passage time model predicts, thus providing better design guideline. Comparison between first passage and last passage time probability density functions are also presented to highlight their differences.