Hybrid PLL system for spin torque oscillators utilizing custom ICs in 0.18 μm BiCMOS

Abstract

This work presents a hybrid and highly adaptive phase locked loop (PLL) system for spin torque oscillators (STO) which are candidates for the next technological implementation of microwave applications. PLL operation is successfully demonstrated in the lower ultra high frequency (UHF) band using a vortex based STO revealing an in-band phase noise of less than −80 dBc/Hz and PLL bandwidth of 2.5 MHz. The system is highly reconfigurable e.g. in terms of the frequency divider ratio N, RF gain and loop gain which makes it robust against device to device variations as well as compatible with a large range of STOs. To the best knowledge of the authors this PLL system utilizing a STO is the first implementation by the use of custom integrated circuits combined with commercial circuits on a board and exhibits the smallest system size and power consumption among the reported STO-PLLs.