The Bra-tenna: A novel body-mounted antenna for off-body communications

This paper presents first how to use the wires of a woman's bra to achieve off-body transmission at 2.4 GHz. The arrangement of the curved wires of a bra is used as a dipole radiating in free space when the length of the wires is progressively increased. The obtained radiation patterns are compared with the radiated fields of straight dipoles having the same length. Then, torso and breast phantoms are numerically created to welcome the curved dipole in close proximity. With several parametric studies, it is demonstrated that even if the radiation efficiency is strongly decreased due to the torso losses, suitable off-body radiation patterns can be obtained for off-body transmissions. Also, different breast implants regarding size and constituent are considered, simulated and evaluated to make this study fully applicable to a wide variety of population. As an alternative to the Bra-tenna and especially if wire-less bras are of concern, a novel Bra-Dielectric Resonator Antenna (Bra-DRA) is introduced providing radiation efficiency 20 times higher than the Bra-tenna still maintaining equivalent radiation patterns in terms of shape. Specific Absorption Rate values are investigated to make sure the safety of the user. The novel so-called Bra-tenna and Bra-DRA could find applications for sensor-based transmission between a women's bra and a smartphone, a set-top box, a WiFi access point or any other smart object.