White paper: Miniaturization of IFA Antenna Using Custom Magnetodielectric Material

The joint work addresses the miniaturization of an Inverted-F Antenna (IFA) operating in the low UHF band (400 MHz), through the development and integration of a custom magnetodielectric material (MDM). The research focuses on the co-optimization of material electromagnetic properties and antenna architecture in order to achieve size reduction while maintaining acceptable bandwidth and radiation efficiency.

Exxelia engineers from the Pessac site, France — Arnaud Naboulet, Aubry Martin, Cécile Vincent, and Christian Ravagnani — actively contributed to the material development, prototyping, and experimental validation phases of the project. Their involvement covered magnetodielectric material processing, metallization techniques, and RF characterization.

Technical approach

The study describes the development of a magnetodielectric material based on hard magnetic hexaferrite compositions (BaxCoyFe24O41). The material was engineered to exhibit elevated permeability in the 300–500 MHz frequency range, combined with controlled magnetic losses and stable temperature behavior. Ferrite components were fabricated using a solid-state process, machined to defined geometries, metallized by silver screen printing, and assembled via epoxy bonding.
 

A dedicated loading strategy was implemented to maximize interaction between the antenna near field and the magnetodielectric material. The influence of material positioning and volume on the resonant strip, short circuit, and feed probe was analyzed with respect to three key parameters: Miniaturization factor & SWR bandwidth & Radiation efficiency

The resulting prototype demonstrates:

• A characteristic radius of λ/15
• An SWR < 3 bandwidth of 20 MHz (approximately 5%)
• A measured radiation efficiency of 30%

The work positions magnetodielectric loading as an alternative to purely dielectric miniaturization techniques, particularly for compact connected objects operating in the UHF band.

The collaboration between Exxelia and CEA-Leti was conducted within the framework of the RAPID FAMTOMAS project financed by the French DGA. This collaboration illustrates Exxelia’s capabilities in advanced functional materials and passive components designed for demanding RF and communication environments.

Beyond magnetodielectric materials, Exxelia specializes in advanced materials and custom designs for RF, microwave, aerospace, defense, and industrial applications. Our expertise spans ferrites, magnetodielectrics, and high-performance ceramics, enabling the creation of components precisely tailored to specific requirements. Leveraging our in-house capabilities, we manufacture our own ceramic powders from basic oxides or carbonates, then press, fire, and machine them to extremely tight tolerances, including advanced surface finishing and polishing.
 

Highlighted product families include:

• Ferrite and magnetodielectric components optimized for frequency-sensitive applications

• High-Q ceramic and mica capacitors for RF tuning and impedance matching

• Film capacitors designed for high voltage operation (up to 1.5 kV) and temperatures up to 140°C

• Custom magnetic components and Microwaves ferrites and dielectric solutions for frequency sensitive applications.

These components are engineered to support compact integration, controlled losses, and stable performance under thermal and electrical constraints, aligning with the requirements of next-generation communication systems.

>> The full technical paper is available for download.