Enhanced Electromagnetic Near Field Probe for Diagnosis and Materials Characterization

This work presents an improved noncontact electromagnetic probe for near-field diagnosis and characterization, driven by a network vector analyzer (VNA) operating in the frequency range of 1 kHz to 1 GHz. Two configurations of a modified near-field microstrip probe (NFMP) are designed and studied, featuring a tip and a dipole termination. Simulations and experimental tests are conducted to assess the probe performances in detecting microcracks. Notably, the detection of cracks of 10 × 20 × 30 μm is achieved by leveraging the shift in resonance frequency. However, the impedance mismatch between the VNA and the probe presents a challenge to the system sensitivity. To address this limitation, a modification is proposed, introducing a surface-adjustable capacitance to the microstrip. This enhancement improves the probe sensitivity and enables full adjustability during measurements. An improvement of 27.13 dB in the reflection parameter is obtained. The developed probes provide nondestructive testing capabilities across a wide frequency range, from 1 kHz to 1 GHz, making them well-suited for integration with VNA systems and facilitating rapid and reliable external measurements.