Dual-Band Dual-Mode Button Antenna for On-Body and Off-Body Communications

Abstract

A dual-band dual-mode button antenna for body centric communications is presented. At the lower band, a spiral inverted-F antenna is designed with omnidirectional radiation pattern for on-body communication. At the upper band, the high-order mode of the inverted-F antenna is utilized together with a metal reflector to realize broadside radiation for off-body communication. For demonstration, a prototype is implemented. The measured peak gains on the phantom at the lower and upper bands are -0.6 and 4.3 dBi, respectively. The antenna operating on the phantom has measured efficiencies of 46.3% at the lower band and 69.3% at the upper band. The issue of specific absorption rate (SAR) is studied. The maximum transmitted power under the SAR regulation of 1.6 W/kg is found to be 26.4 dB·m, which is high enough for body centric communications. In addition, the transmission performance between two proposed antennas mounted on the body is investigated by measuring the transmission loss. With an overall miniaturized size, the robust button antenna could be integrated in clothes and be a potential candidate for wireless body area network applications.

Smart Textile‐Integrated Microelectronic Systems for Wearable Applications

“…Antenna is an essential component in wireless communication modules. To fulfill the specific requirements for wearable applications, it requires planar and flexible textile substrates . The performance of a planar microstrip antenna largely depends on the permittivity and thickness of the textile substrate, which directly affect its efficiency and bandwidth .…”

Design of a dual band dual mode antenna for on/off body communications

“…Another option is to achieve the dual mode antennas where one mode is used for on body applications, and the other for off body applications. The schematic of the on/off body communication applications is illustrated in Figure , where the lower frequency is used for on body communication for its lower shadow fading and stronger diffraction with longer wavelength, while the higher frequency is used for off body communication to be aimed for higher gain and lower back lobe . The designs in References achieve dual band and dual mode operation with the radiation pattern being broadside at lower frequency and omnidirectional at higher frequency.…”

“…But the lower band is quite sensitive to human body as the ground also contributes to the radiation. The button PIFA antenna proposed in Reference provides dual band dual mode operations, but its SAR value at higher band is quite high. Considering the limitations of all the existing on/off body dual mode antenna designs, there is a need to investigate a dual mode antenna with low link loss, low influence from human body as well as low SAR values.…”

“…For the on/off body communication systems, the antennas must have the capability of operating in dual radiation modes where one mode is used for on body applications, and the other for off body applications. A number of antennas have been proposed for WBAN systems, [1][2][3][4][5][6][7][8][9][10][11][12] but their overall performances still have room to improve.…”

“…The schematic of the on/off body communication applications is illustrated in Figure 1, where the lower frequency is used for on body communication for its lower shadow fading and stronger diffraction with longer wavelength, while the higher frequency is used for off body communication to be aimed for higher gain and lower back lobe. 7,8 The designs in References 9-11 achieve dual band and dual mode operation with the radiation pattern being broadside at lower frequency and omnidirectional at higher frequency. This arrangement, however, suffers from high link loss and is not suitable for on/off body communication.…”