Microwave Photonics-Based Reflectometry for PCB Defect Detection

In this study, a microwave photonic-based step frequency reflectometry (MPSR) system is proposed to perform PCB defect detection, which incorporates photonic techniques on wideband step frequency (SF) signal generation to reflectometry implementation. An optical recirculating frequency shift loop (OFSL) is utilized to expand the spectral bandwidth of the input signal transmitted to the device under test (DUT). Coherent mixing process of the DUT's response signal with the incident signal enables the accurate extraction of the DUT's frequency response. Subsequently, the location information of defects, which usually manifested as impedance discontinuity within the DUT, can be extracted from this frequency response under inverse Fourier transform. Simulations of electronic and photonic systems are used to analyze the performance of the proposed concept. The simulation results are in well agreement with the Advanced Design system (ADS) simulation, demonstrating the feasibility of the proposed system in determining PCB defects.