No abstract

No abstract

We address the question of the optimal choice of loading material for antenna miniaturization.A new approach to identify the optimal loading material, dielectric or magnetic, is presented for resonant antennas. Instead of equivalent resonance circuits or transmission-line models, we use the analysis of radiation to identify the fields contributing mostly to the stored energy. This helps to determine the beneficial material type. The formulated principle is qualitatively illustrated using three antenna types. Guidelines for different antenna types are presented. IntroductionDemand towards smaller and smaller portable communication devices has continuously challenged antenna engineers to come up with solutions to make the antennas smaller. However, the task has not been trivial since especially bandwidths of antennas are not always allowed to decrease. Resonant antennas, the type used e.g. in most if not all hand-held devices, can be made to operate at lower frequencies by making their electric lengths larger. This can be easily achieved by inserting some material to the structure so that the resonating wavelength decreases. Of course, when the fields in the resonators are changed, the operation of the antenna is not only changed in view of the resonance frequency but also the bandwidth, matching, efficiency, etc. are affected. Miniaturization of patch antennas using materials with various material parameters and µ studied in [1] aroused discussion of the benefits of different materials with magnetic response. Various loading scenarios have been considered, for example, dielectric coated dipole antennas were experimentally and theoretically studied in [2], dipole antennas covered with metamaterials were studied in [3], and double negative materials for electrically small antennas in [4]. In this article, we discuss how to determine the proper loading material for a small resonant antenna. Especially, arXiv:0907.2132v1 [physics.class-ph]

No abstract

No abstract