Phase Noise in Networks of Mutual Synchronized Spatially Distributed 24-GHz PLLs

This article discusses the phase noise (PN) characteristics of mutually delay-coupled phase-locked loop (PLL) nodes operating at 24 GHz. It examines the effect of mutual synchronization on PN. A behavioral model is derived that describes the critical dynamics of synchronized nodes. Power spectral density (PSD) measurements of mutually synchronized PLL nodes show that mutual coupling improves the PN, while unidirectional coupling increases the PN by about 3 dB per additional node. The long-term stability of the frequencies of individual nodes within the network is also studied, and no significant frequency differences are observed in stable synchronized states. This research shows that the time delay between nodes has no significant effect on the PN, but only on the synchronized state and its characteristics. The network topology also affects the dynamics, with different improvements in PN depending on the topology. The maximum improvement observed is 14.48 dB. Overall, the results suggest that mutually delay-coupled PLL nodes have the potential to provide stable, accurate, and robust synchronization in a range of applications, such as spatially distributed Internet of Things (IoT) devices and sensors. For research on advanced technologies that require precise and synchronized communications, these results have significant implications.