Separation and imaging of mixed signals on microwave chips based on nitrogen-vacancy color center microscopy

Microwave chips are widely utilized in modern communication, national defense, and various technological domains. However, effective signal identification remains challenging due to complex multi-frequency microwave interference. To address this issue, we propose an advanced optical imaging framework based on nitrogen-vacancy (NV) center near-field microscopy. This framework enables the separation and imaging characterization of mixed multi-frequency microwave signals across a wide field of view (2000 μm ×1600 μm , spatial resolution of 5 μm) on chip surfaces. By leveraging the NV color center as a mixer, combined with a multi-frequency hybrid model and fast Fourier transform (FFT) analysis, we convert the invisible electromagnetic waves into visible optical information. Using a wide-field microscopy system equipped with a high-speed optical camera, our approach effectively enables the separation and imaging of mixed microwave signals across two complex scenarios. Comparative analysis with finite element simulation validates the accuracy of this approach. Experimental results reveal mHz frequency resolution for GHz microwaves and μT-level signal intensity resolution, showcasing its superior capability for imaging mixed signals with multi-frequency. These findings provide critical technical support for microwave chip characterization, interference signal identification, and diagnostic testing, highlighting the broad applicability of this technique.