Dual-Tuned Floating Solenoid Balun for Multi-nuclear MRI and MRS

Motivation: Conventional baluns for multi-nuclei MRI and MRS applications require extensive space and numerous components, resulting in complex soldering processes. Goal(s): Developing dual-tuned and float balun with minimum size and great common-mode current reduction ratio (CMRR). Approach: A double-layer solenoidal design was implemented to maximize mutual inductance, with a floating configuration that reduces overall dimensions, while incorporating a pole-insertion circuit to achieve the second resonance frequency. Results: The CMRR reached -21.1 dB at 78.6 MHz and -26.8 dB at 298 MHz which indicates 99% common-mode current is suppressed with the balun dimension 16mm in diameter and 24mm in length for RG-174 alike cable design. Impact: This balun design effectively reduces the space requirements and component count for multi-nuclei MRI and MRS. It achieves excellent CMRR across various cable types and can be tuned to different resonant frequencies, thereby enhancing patient safety and maintaining signal integrity.