H-Field Probe with Active Balun for MRI-Conditional Testing of Medical Devices

摘要

This work presents the design and construction of a H-field probe with active balun for MRI (magnetic resonance imaging) conditional testing of medical devices. The H-field probe was designed using a small loop antenna with 2 mm radius to have high spatial resolution and sensitivity. It was tuned and matched at a center frequency of 128 MHz, which corresponds to 3 T MRI systems or equivalent RF exposure systems. An active balun with a gain 18.28 dB and noise figure of 0.5 dB was employed to boost the detected H-field signal level. The designed Hfield probe and active balun have been fabricated on a doublesided printed circuit board (PCB), FR4 thickness of 1.57 mm and a copper thickness of 35 μm, with overall footprint of 22 mm × 11 mm.