Abstract
The human body is an extremely challenging environment for wearable antennas due to the complex antenna-body coupling effects. In this article, a compact flexible dual-band planar meander line monopole antenna (MMA) with a truncated ground plane made of multiple layers of standard off-the-shelf materials is evaluated to validate its performance when worn by different subjects to help the designers who are shaping future complex on-/off-body wireless devices. The antenna was fabricated, and the measured results agreed well with those from the simulations. As a reference, in free-space, the antenna provided omnidirectional radiation patterns (ORP), with a wide impedance bandwidth of 1282.4 (450.5) MHz with a maximum gain of 3.03 dBi (4.85 dBi) in the lower (upper) bands. The impedance bandwidth could reach up to 688.9 MHz (500.9 MHz) and 1261.7 MHz (524.2 MHz) with the gain of 3.80 dBi (4.67 dBi) and 3.00 dBi (4.55 dBi), respectively, on the human chest and arm. The stability in results shows that this flexible antenna is sufficiently robust against the variations introduced by the human body. A maximum measured shift of 0.5 and 100 MHz in the wide impedance matching and resonance frequency was observed in both bands, respectively, while an optimal gap between the antenna and human body was maintained. This stability of the working frequency provides robustness against various conditions including bending, movement, and relatively large fabrication tolerances.
Highlights
Advances in the miniaturization of wireless devices and designs of smart wireless networks have allowed a rapid development in wireless body area networks (WBAN) because of their vast demands for numerous applications such as those in healthcare, the military, sports, and electronic gaming [1]
It can be seen that the wearable antenna demonstrates omnidirectional radiation at the lower band, which can be used for on-body communication
The proposed antenna was evaluated to validate its performance in various scenarios such as in free-space and on the body with different sizes and under different bending radii and wet conditions
Summary
Wearable antennas must be designed and characterized carefully in order to maintain a reliable communication link even under the detuning effects of lossy body tissues, because the human body can deteriorate the performance of the antenna [4]. We have shown that the results are not sensitive to the presence of the human body, and insignificant detuning is observed at both bands when a 10 mm distance was maintained These evaluations are influential in determining proper antenna operation on the human body, and pave the way for unique designs as mentioned by Guy A. Small size, use of frequency selective surface might make it difficult to fabricate, single band, not fully tested on the body and under bending.
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