Miniaturizing Antennas with Magnetic Materials

Miniaturizing Antennas with Magnetic Materials

Feb. 20, 2019
As researchers from Greece discovered, ferrimagnetic materials provide a starting point for smaller antennas with greater range.

Antennas are the beginning and ending points for many systems and with a growing number of wireless applications, there’s a greater demand for efficient, miniature low-profile antennas. In pursuit of such components, Evmorfili Andreou and three fellow researchers from Athens, Greece have explored the use of magnetodielectric materials with tunable permeability for reconfigurable antenna designs.

Magnetodielectric materials exhibit relative permittivity (εr) and relative permeability (µr) of greater than one. By using a magnetodielectric substrate material with moderate values of permittivity and permeability, it’s possible to miniaturize an antenna as much as when using a dielectric substrate material with a considerably higher value of εr.

The researchers noted the constant need for antennas capable of adjusting operating characteristics to adapt to changing channel conditions. Tunable materials such as ferroelectric and ferromagnetic substrates can provide excellent starting points for wideband antenna designs, especially magnetic materials with high resistivity for high-frequency antennas.

Ferrimagnetic oxides have unique properties when a magnetic field is applied, making them suitable for antennas and other microwave components. Ferrimagnetic oxides, with iron oxide as their main component, are classified as spinels, garnets, and hexaferrites. Garnets are typically employed for components from 1 to 10 GHz, spinels are commonly used for applications from 3 to 30 GHz while hexaferrites are used for higher-frequency designs, as high as 100 GHz. Ferrites typically have high permittivity and low dielectric losses, with flexible magnetic properties.

When modeling the properties of ferrimagnetic materials, such as permeability, magnetic flux density, magnetic field strength, and resonance linewidth, it’s the magnetic bias field that controls the switching of the material between two magnetization states. For example, different materials can be considered partially magnetized or magnetically saturated, and the approach to simulating this parameter will differ for the various ferrimagnetic materials.

The researchers explain their approach to simulating the different materials and choosing a ferrimagnetic material for a reconfigurable antenna design. Material selection depends on the target frequency range of the antenna. Simulation with electromagnetic (EM) modeling software involves computing material parameters, such as permeability, in the “off” and “on” states of the material (without and with magnetic field applied). By dividing their yttrium iron garnet (YIG) material sample into different zones for study, the magnetic field distribution can be precisely calculated. The modeled antenna performance from approximately 4.6 to 5.5 GHz closely matches the measured performance for a fabricated component.

See “Magnetodielectric Materials in Antenna Design,” IEEE Antennas & Propagation Magazine, Vol. 61, No. 1, February 2019, pp. 29-40.

About the Author

Jack Browne | Technical Contributor

Jack Browne, Technical Contributor, has worked in technical publishing for over 30 years. He managed the content and production of three technical journals while at the American Institute of Physics, including Medical Physics and the Journal of Vacuum Science & Technology. He has been a Publisher and Editor for Penton Media, started the firm’s Wireless Symposium & Exhibition trade show in 1993, and currently serves as Technical Contributor for that company's Microwaves & RF magazine. Browne, who holds a BS in Mathematics from City College of New York and BA degrees in English and Philosophy from Fordham University, is a member of the IEEE.

Sponsored Recommendations

Wideband MMIC LNA with Bypass

June 6, 2024
Mini-Circuits’ TSY-83LN+ wideband, MMIC LNA incorporates a bypass mode feature to extend system dynamic range. This model operates from 0.4 to 8 GHz and achieves an industry leading...

Expanded Thin-Film Filter Selection

June 6, 2024
Mini-Circuits has expanded our line of thin-film filter topologies to address a wider variety of applications and requirements. Low pass and band pass architectures are available...

Mini-Circuits CEO Jin Bains Presents: The RF Engine of the 21st Century

June 6, 2024
In case you missed Jin Bains' inspiring keynote talk at the inaugural IEEE MTT-S World Microwave Congress last week, be sure to check out the session recording, now available ...

Selecting VCOs for Clock Timing Circuits A System Perspective

May 9, 2024
Clock Timing, Phase Noise and Bit Error Rate (BER) Timing is critical in digital systems, especially in electronic systems that feature high-speed data converters and high-resolution...