Low SAR Ferrite Handset Antenna Design

• Published in: IEEE transactions on antennas and propagation Vol. 55; no. 4; pp. 1155 - 1164
• Main Authors: Kitra, M.I., Panagamuwa, C.J., McEvoy, P., Vardaxoglou, J.C., James, J.R.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2007; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; Antenna design; Antennas; Applied sciences; Cell phones; Computer simulation; Efficiency; Equipments and installations; Exact sciences and technology; Ferrite; Ferrite loaded antennas; Ferrites; Geometry; Inclusions; Loaded antennas; Mobile radiocommunication systems; multiband; Permittivity; Radiocommunications; Radiorelay links; Services and terminals of telecommunications; Slabs; Solid modeling; specific absorption rate (SAR); Studies; Synthetic aperture radar; Systems, networks and services of telecommunications; Telecommunications; Telecommunications and information theory; Telephone sets; Telephone. Videophone; Transmission line antennas; Transmission line matrix methods; wireless handset; Performance evaluation; Positioning; Mobile phone; Wireless telecommunication; wireless handset; Optimization; specific absorption rate (SAR); Accuracy; Permittivity; Mobile radiocommunication; GSM system; Bluetooth technology; Radio link; Lossy medium; Translation motion; Specific absorption rate; Coated material; Simulation; Ferrite loaded antennas; Multifrequency antenna; Analytical method; Monopole antenna; UMTS system; Feasibility; multiband; TLM method
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2007.893370

The benefits resulting from the inclusion of ferrite in material loaded antennas are investigated, initially through the use of a spherical analytic model and then through a transmission line matrix simulation tool applied to a rectangular slab geometry. It is observed that a material with equality of relative permittivity and permeability in combination with specific positioning of the antenna in relation to the head, can result in the definitive small-size, high efficiency and bandwidth, low specific absorption rate (SAR) antenna. The accuracy of the simulations is validated both through efficiency and SAR measurements of three material coated monopole samples. Further research into optimizing the above attributes and translating them into a handset antenna leads to a multiband antenna design covering the GSM 1800, 1900, UMTS and Bluetooth bands, with a SAR value reduced by 88% compared to conventional phones and an efficiency of 38% at 1.8 GHz. A tri-band antenna design is also presented, utilizing currently available lossy ferrite material and it is considered as the first step towards the feasibility of the ultimate low SAR multiband ferrite handset antenna, until further material development specifically for antenna applications takes place