Coupling element based mobile terminal antenna structures

In this paper, internal low-volume antenna structures for mobile terminals are studied. The work concentrates on the possibilities to reduce the volume of mobile terminal antenna elements by efficiently utilizing the radiation of the currents on the mobile terminal chassis. Essentially nonresonant coupling elements are used to optimally couple to the dominating characteristic wavemodes of the chassis. The antenna structures are tuned to resonance with matching circuits. During the last few years, the approach has achieved growing interest-also among industrial manufacturers of mobile terminals. There exist, however, no systematical feasibility and performance studies of the idea. During the work, two antenna models with very low-volume coupling elements are designed and in total four prototypes are constructed. The simulation and measurement results show that the studied antenna concept is a very promising alternative for traditional antenna technologies. The presented analysis provides useful and novel information for the designs of the future low-profile and low-volume mobile terminal antennas.