Planar Elliptical Coil Design With Helmholtz Structure Having a Uniform Magnetic Field for Nuclear Magnetic Resonance Spectroscopy

Abstract

This paper presents the design and simulation of a novel planar elliptical coil for nuclear magnetic resonance (NMR) spectroscopy, fabricated as a printed circuit board (PCB) with an FR4 substrate. This technique offers valuable insights into molecular dynamics, structure, and interactions. A uniform magnetic field for spin excitation is generated by coupling two elliptical coils in a Helmholtz arrangement. The proposed coil stands out as an innovative alternative to traditional coils due to its improved efficiency, precise design, and reduced weight and spatial requirements. This work focuses primarily on the results obtained from finite element method (FEM) simulations. These simulations demonstrate a magnetic field uniformity of 92% across a broad frequency range (1–10 MHz), achieved through optimized tuning and matching capacitors. The maximum uniform magnetic flux density recorded within this frequency range is 220 μT. Furthermore, S11 and S21 parameters, along with the electric and magnetic field distributions, are calculated and analyzed to characterize RF signal interaction with the system. A detailed analysis of the S-parameters reveals optimal coil matching and tuning, minimizing energy losses. Ultimately, these results confirm the suitability of the proposed coil for portable NMR spectrometers, highlighting the simulation-driven design approach. This innovative design, with its significantly reduced weight, size, and manufacturing cost, promises considerable advancements in portable NMR spectroscopy.