A distributed amplitude control loop for VCO-array-based EPR-on-a-chip detectors

This paper presents an amplitude control loop (ACL) for VCO-array-based electron paramagnetic resonance (EPR) detectors. The proposed ACL enhances the microwave magnetic field (B1) stability over the whole VCO frequency sweep range, against different sample environments and at varying experimental conditions. By introducing a distributed amplitude detection scheme, the proposed ACL implementation can regulate B1 field intensities in injection-locked VCO arrays with reduced loading effects and minimal phase noise degradation. Extracted-level circuit simulations on an example VCO array implementation demonstrate the functionality and excellent achievable performance of the proposed approach.