Anisotropic magneto-dielectrics for wideband planar antenna miniaturization applications

Summary form given only: In this paper, the application of magneto-dielectric materials and their anisotropic electromagnetic properties for designing wideband planar antennas with small form factors is studied. At the lower UHF band (~300 MHz), the sizes of antennas are rather large and oftentimes antennas with wide bandwidth have 3-D structures. For many modern military applications planar structures with low profile is of great interest. In the area of planar antenna miniaturization, application of high permittivity materials as substrates has been studied by many researchers. However, high permittivity materials tend to reduce the antenna bandwidth and lower the radiation efficiency. Impedance matching of the antenna also becomes difficult due to the large capacitive nature of high permittivity materials. On the other hand magnetic materials at VHF and UHF bands tend to be lossy due to the proximity of ferrite magnetic resonances to the desired operational frequencies. In this presentation, composite magneto-dielectric materials are proposed as a way to control the material loss while maintain a high index of refraction with almost equal permittivity and permeability. Magneto-dielectrics can be made up of dielectric and magnetic materials that are arranged in different periodic configurations. Different periodicity arrangements, orientation, and volume fraction ratios provide much flexibility in designing anisotropic medium for a desired antenna. When used as substrates for planar antennas, the magneto-dielectric can also miniaturize the antenna using moderate values of effective permittivity and permeability simultaneously. With the lower effective loss factor, the antenna radiation efficiency can be improved. Moreover, since the characteristic impedance of the magneto-dielectric is close to that of a free space, the antenna impedance matching in a wide frequency range will become less difficult. Different antenna configurations with different magneto-dielectr- c composite materials will be considered and the resulting antenna performance will be compared with dielectric only materials have the same index of refraction.