On-body Efficiency Research Articles

Design of Low-SAR and High On-Body Efficiency Tri-Band Smartwatch Antenna Utilizing the Theory of Characteristic Modes of Composite PEC-Lossy Dielectric Structures

A low specific absorption rate (SAR) and high on-body efficiency tri-band smartwatch antenna is designed utilizing the theory of characteristic modes (TCM) of composite perfect electric conductors and lossy dielectric structures. The antenna works in the GPS frequency band, WLAN 2.4 GHz/Bluetooth frequency band, and 5G frequency band. After analyzing the characteristic modes of the antenna and human body in the above three frequency bands, the characteristic modes with small modal coupling coefficients (MCCs) are selected and excited. Due to the small mutual coupling between the antenna and the human body, the proposed antenna has good performance on both SAR and on-body efficiency. Its measured 10 g average body SAR is lower than 1.3 W/kg. When it is placed 0 mm above the body, its on-body efficiency is 9.3%–9.88% in the GPS frequency band, 12%–14.2% in the WLAN 2.4 GHz/Bluetooth frequency band, and 17.3%–20.1% in the 5G frequency band.

A Novel Design and Study of a Self-Complimentary Miniaturized Millimeter Wave Antenna for Body-Centric Networks

A new self-complimentary compact antenna operating at 60 GHz within the millimeter wave frequency range has been presented in this paper. The design is intended for the wireless body-centric network (WBCN). The proposed compact design has a dimension of 4.5 × 6.03 × 1.59 mm3. The antenna was designed with multiple geometrical structures held upon a narrow feed line with a rectangular slot and parasitic elements to increase bandwidth. Free space simulations of the antenna produced optimistic results in terms of gain, radiation efficiency, and bandwidth; a maximum gain of 6.7 dB was achieved with an efficiency of 84.5%. Parametric studies were carried out to better understand its nature by modifying the key design aspects and comparing the outcomes. A 3D human torso phantom was virtually created with natural human body properties, and the on-body performance of the design was tested by placing the antenna in its near field. With some slight deviation from their peak performance, on-body simulations displayed better results in most of the cases. The antenna was positioned five different gaps from the torso for future investigations. The result of the distance-based study was amazingly good as the antenna performance was consistent throughout all distances. 10.77 GHz of bandwidth is found for the closest distance to the human torso, while the on-body radiation efficiency is also outstanding; the minimum radiation efficiency recorded is 73.78 when the antenna is just a couple of millimeters away. Overall, the comparison shows that the antenna worked best when it was placed only 2 mm apart from the body. Investigation indicates the antenna is a promising candidate for BCN applications because of its wider bandwidth and better on-body efficiency.

Suspended embroidered triangular e-textile broadband antenna loaded with shorting pins

An embroidery triangular e-textile (electronic textile) antenna with shorting pins is proposed in this paper for broadband response and to increase the on-body efficiency in 5.8 GHz industrial, scientific, and medical (ISM) band. The triangular patch is embroidered with silver coating conductive yarn using a computerised aided embroidery machine. The proper positioning of the shorting pins is selected to tune the fundamental TM10 mode at the desired frequency. The proposed antenna is embroidered on the textile substrate material and is suspended over a slotted ground plane to realize wider bandwidth. The antenna yields measured impedance bandwidth of 210 MHz (5.63–5.84 GHz) for S11 ≤ -10 dB with a peak gain of 4.1 dB in the broadside direction. Furthermore, the radiation efficiency of the antenna is above 65% over the operating bandwidth. The effect of an antenna radiation on the human body is also analysed by evaluating the specific absorption rate (SAR) levels. The broadband embroidery triangular patch antenna with broadside radiation pattern provides the attractive flaunt and best fit device for off body communication.

The Design of a Reconfigurable Slot Antenna Printed on Glass for Wearable Applications

A novel pattern and polarization reconfigurable wearable slot antenna suitable for smart glasses is proposed. The antenna is designed and fabricated on glass and reconfiguration is realized using four PIN diodes. It operates in the 2.4 GHz Industrial, Scientific and Medical Band. It consists of an equilateral L-shaped slot fed by a single coplanar waveguide feed. The slot is manipulated with switches to generate two modes of operation. Each mode corresponds to one of the two states of the switches which result in different L-shaped slots with unequal legs creating patterns that are polarized in perpendicular to each other. The antenna has been shown to perform well near the human body using numerical and physical phantoms. The correlation between the two modes is calculated to be less than 0.04 with 41% and 56% on-body efficiency for each mode. The Specific Absorption Rate is shown to be well below the limit specified in the European Standards through simulations.

IMPACT OF FEEDING LOCATION ON ON-BODY PERFORMANCE OF SMALL ON-GROUND ANTENNAS

In this paper, three commonly used on-ground antenna types (loop, monopole and planar inverted-F antenna) are compared in the scope of wireless body area networks (WBAN) for on-body communications at 2.45 GHz. The bandwidth of the antennas can be enhanced by placing them towards the edge or the corner of the small ground plane (25× 35 mm 2 ) which has, as a consequence, detrimental effects on radiation characteristics that motivates the examination of the impact of feeding location for on-body propagation in detail. The present study quantifies the trade-off between on-body efficiency, the gain in the direction tangential to the surface, applicability to launch creeping waves and bandwidth potential of the different antenna types with various feeding locations. The simulated channel gain |S21| around tissue-equivalent numerical phantoms is compared to an analytical WBAN path loss model.

Wearable Endfire Textile Antenna for On-Body Communications at 60 GHz

A textile endfire antenna operating in the 60-GHz band is proposed for wireless body area networks (BANs). The permittivity of the textile substrate has been accurately characterized, and the Yagi-Uda antenna has been fabricated using an ad hoc manufacturing process. Its performance in terms of reflection coefficient, radiation pattern, gain, and efficiency has been studied in free space and on a tissue-equivalent phantom representing the human body. It is shown that the antenna is matched in the 57-64-GHz band. Its measured on-body efficiency and maximum gain equal 48.0% and 11.9 dBi, respectively. To our best knowledge, this is the first textile antenna for on-body wireless communications reported at millimeter waves.