##### Magnetodielectric Materials

Magnetodielectric materials are of both nontrivial or designed/tailored permittivity εr0 and magnetic permeability μr0. Magnetodielectric materials are widely used in the miniaturization of RF devices and in applications that require a material with a tailored impedance. The reason for using magnetodielectric materials, instead of dielectric materials, can be seen from the following table:

Dielectric Materials Magnetodielectric Materials
Miniaturization $\sqrt { \varepsilon }$ $\sqrt { \varepsilon \mu }$
Impedance Match $\sqrt { 1/\varepsilon }$ $\sqrt { \mu /\varepsilon }$
Antenna BW $\ 1/\varepsilon$ $\ 1/\varepsilon$

In principle, the physical dimensions of an active antenna can be reduced by compressing the wavelength of the electromagnetic wave inside the materials, leading to a miniaturization factor. Therefore both dielectric permittivity ε and magnetic permeability μ have the same effect of compressing the electromagnetic wavelength inside the materials. Another important parameter is that magnetodielectric materials can be used in patches, microstrips, and spiral antennae, etc. In addition to miniaturization, the usage of magnetodielectric materials in antennae can improve the impedance matching and enhance the bandwidth.

For example, consider a typical patch antenna operating at 300MHz with conventional non-magnetic dielectric materials (ε=2.56, μ=1). By using a magnetodielectric material (ε=7, μ=7), the length of antenna can be reduced to 1/4 of the original size. In order to achieve a similar factor of miniaturization, a high dielectric material (ε=49, μ=1) is required. However, doing so leads results in much lower impedance and a narrower bandwidth

###### Spectrum Magnetic Magnetodielectric Ferrites

Spectrum Magnetics LLC has developed three types of SMMDF materials: SMMDF1xx, SMMDF2xx, and SMMDF3xx. These ceramic tiles have good mechanical strength, high permeability and permittivity, and are stable in most environments.

SMMDF1xx has the highest matched permeability and permittivity of 15 in a broad frequency range. It can be used in the frequency ranges of 30MHz to 800MHz. SMMDF1xx has good mechanical properties, and can be machined or fabricated in various shapes (disk, ring, bar, square tiles, etc.) or sizes (up to 4″x4″x1″cm, minimum thickness of 2mm).

SMMDF2xx has the lowest magnetic loss tangent of 0.1 at 1GHz with a permeability of of 4-7 and permittivity of 9-15. It can be used in the frequency ranges of 30MHz to 2,000MHz. SMMDF2xx has good mechanical properties, and can be machined or fabricated in various shapes (disk, ring, bar, square tiles) or sizes (up to 4″x4″x1″cm, minimum thickness of 2mm).

SMMDF3xx has a permeability (15-100) higher than its permittivity (~12) in a broad frequency range. It can be used in the frequency ranges of 30MHz to 500MHz. SMMDF3xx has good mechanical properties, and can be machined or fabricated in various shapes (disk, ring, bar, square tiles) or sizes (up to 4″x4″x1″cm, minimum thickness of 2mm).

The above materials are also available in polymer composite (SMMDP series) forms, allowing for lighter and more flexible antenna designs.

Product ID µ’ @ 10MHz ε’ @ 10MHz µ”/µ’ @ 10MHz µ”/µ’ @ 100MHz µ”/µ’ @ 500MHz µ”/µ’ @ 1GHz Datasheet
SMMDF100 10 10 0.003 0.03 0.2 0.7 SMMDF100
SMMDF101 15 15 0.01 0.03 0.2 2 SMMDF101
SMMDF200 4 10 <0.001 0.008 0.04 0.1 SMMDF200
SMMDF201 7 15 0.01 0.02 0.09 0.3 SMMDF201
SMMDF300 230 12 0.3 1.4 5.6 35 SMMDF300
SMMDF301 16 12 <0.001 0.005 1.2 3.2 SMMDF301
SMMDF302 42 13 0.004 0.7 2.1 4.3 SMMDF302
SMMDP100 3 6 <0.001 0.003 0.05 0.2 SMMDP
SMMDP101 5 8 <0.001 0.006 0.08 0.45 SMMDP
SMMDP200 2 7 <0.001 <0.001 0.03 0.05 SMMDP
SMMDP300 7 6 <0.005 0.2 0.5 0.7 SMMDP
SMMDP301 10 7 0.01 0.25 0.6 1 SMMDP
SMMDP400 1.5 3.3 <0.001 <0.001 0.06 0.08 SMMDP
SMMDP401 2.1 5.4 0.01 0.03 0.1 0.15 SMMDP