Resolution of phase difference and frequency measurements of mutually injection-locked oscillators for resonant sensing applications

Sensor architectures based on coupled resonators are receiving increased interest from the resonant sensing community. This is first motivated by the fact that such architectures can provide differential measurements of the physical quantity of interest, without being hampered by spurious couplings between the resonant elements. Furthermore, certain output metrics of such sensors have an increased sensitivity to the measure and, compared to conventional resonant sensors with frequency-modulated outputs. We have recently demonstrated that this gain in sensitivity did not necessarily entail a gain in sensor resolution. In this paper, we investigate this issue further, and provide a first experimental proof of our theoretical result, using CMOS-MEMS monolithically-integrated mutually injection-locked oscillators (MILOs).