MICROSTRIP ANTENNAS have been miniaturized through a number of techniques and choices of materials. Traditional techniques involve the use of high permittivity dielectric materials to decrease the physical dimensions of the radiator. Pekka Ikonen and associates from the Radio Laboratory/SMARAD at the Helsinki University of Technology (Helsinki, Finland) chose an approach using artificial magnetodielectric loading to create artificial magnetism at microwave frequencies for a net reduction in the size of a microstrip antenna.
The researchers note that resonant magnetic media can be used with planar radiators in two basic ways. If the resonance of the material lies inside the operational band of the loaded antenna and can be combined with the antenna resonance, it is possible to create a multiresonant antenna. Another method involves using the material-to resonate at a higher frequency than the operational frequency of the loaded antenna, while maintaining the effective magnetic properties over a wide frequency band.
The researchers systematically studied the effects of artificial magnetodielectric substrates on the impedance bandwidth properties of microstrip antennas and built a prototype antenna having volume loaded with an array of metasolenoids. Designed for 2.07 GHz, the antenna employed a host substrate of R/T Duroid material from Rogers Corp. (Rogers, CT) and achieved a fairly large radiation quality factor for its relative small size of 35 35 7.5 mm. See "On Artificial Magnetodielectric Loading for Improving the Impedance Bandwidth Properties of Microstrip Antennas," IEEE Transactions on Antennas and Propagation, June 2006, Vol. 54, No. 6, p. 1654.