Variation Range of Different Inductor Topologies with Shields for RF and Inductive Sensing Applications

Area of Science:

• Electrical Engineering
• Electromagnetics
• Materials Science

Background:

• Planar inductors are crucial components in modern electronic devices, especially in inductive sensing and radio-frequency (RF) applications.
• The performance of planar inductors can be significantly affected by nearby conductive or magnetic materials, such as shielding plates.
• Understanding these interactions is vital for optimizing inductor design and device functionality.

Purpose of the Study:

• To investigate the impact of ferromagnetic (Fe-based) and conductive (Cu-based) shield plates on the characteristic parameters of various planar inductor topologies.
• To determine the range of variation in inductance, resonant frequency, resistance, and quality factor (Q-factor) when shield plates are brought near different inductor designs.
• To identify optimal planar inductor designs and shielding strategies for enhanced performance in sensing and RF applications.

Main Methods:

• Fabrication of five distinct square planar inductor topologies (spiral, tapered, non-spiral, meander, fractal) on printed circuit boards (PCBs).
• Experimental assessment of inductor parameters (inductance, resonant frequency, Q-factor, resistance) at a working frequency of 1 MHz with varying proximity to Fe-based and Cu-based shield plates.
• Analysis of the influence of shield plate proximity and material on inductor characteristics, including the phenomenon of ferromagnetic resonance (FMR).

Main Results:

• Inductance decreased with Cu-based plates and increased with Fe-based plates, with double-layer topologies showing up to a 60% variation near Cu.
• Ferromagnetic resonance (FMR) was observed, causing inductance to decrease near Fe-based plates beyond a critical frequency, with FMR frequency dependent on topology.
• Q-factor decreased for all topologies, particularly with Fe-based plates due to increased track resistance from FMR. Resonant frequency shifts varied based on topology and layer configuration.

Conclusions:

• Metal shielding plates offer a viable method for tuning planar inductor characteristics, presenting significant potential for nondestructive sensing and RF applications.
• The choice of shielding material (Fe vs. Cu) and inductor topology (e.g., double-layer spiral) critically influences performance parameters like inductance and Q-factor.
• This study provides valuable insights for designing advanced inductive sensors and RF components by leveraging controlled electromagnetic interactions with shielding materials.