The Simulation of the Closed-Loop Frequency Tracking Control Based on the Diamond Nitrogen-Vacancy Center

Due to its inherent magnetic sensitivity, the nitrogen-vacancy (NV) center in diamonds enables magnetic field measurements. Compared with traditional methods, the NV center offers significant advantages in sensitivity, stability, and operating temperature range. Currently, NV-based magnetic field measurement techniques are mainly divided into frequency-sweeping and fixed-frequency methods. The frequency-sweeping method provides higher measurement accuracy but requires a longer measurement period, making it unsuitable for fast measurements. The fixed-frequency method, which maintains a constant micro-wave frequency to rapidly reflect magnetic field changes, may suffer from harmonic distortions, and its dynamic range is constrained by the linewidth of the optically detected magnetic resonance (ODMR) spectrum. To address these issues, this paper adopts a closed-loop frequency tracking control approach, dynamically adjusting the micro-wave source's frequency to track the resonance frequency in real time under an external magnetic field. Using this method, we developed a simulation model of the closed-loop system in MATLAB, comparing the tracking performance of the linear slope control and the PID control. The simulation results demonstrate that the closed-loop frequency tracking approach based on the PID control exhibits superior tracking performance for magnetic field measurements. These findings contribute to improving the sensing performance of the NV center as a sensitive element in measurement systems.