Abstract
In this article, a graphene-assembled film (GAF)-based compact and low-profile ultra-wide bandwidth (UWB) antenna is presented and tested for wearable applications. The highly conductive GAFs (~106 S/m) together with the flexible ceramic substrate ensure the flexibility and robustness of the antenna, which are two main challenges in designing wearable antennas. Two H-shaped slots are introduced on a coplanar-waveguide (CPW) feeding structure to adjust the current distribution and thus improve the antenna bandwidth. The compact GAF antenna with dimensions of 32 52 0.28 mm3 provides an impedance bandwidth of 60% (4.3–8.0 GHz) in simulation. The UWB characteristics are further confirmed by on-body measurements and show a bending insensitive bandwidth of ~67% (4.1–8.0 GHz), with the maximum gain at 7.45 GHz being 3.9 dBi and 4.1 dBi in its flat state and bent state, respectively. Our results suggest that the proposed antenna functions properly in close proximity to a human body and can sustain repetitive bending, which make it well suited for applications in wearable devices.
Highlights
Wearable wireless technologies have been attracting increasing attention for solving the conformal problem between wearable antennas and clothes [1,2]
Our results suggest that the proposed antenna functions properly in close proximity to a human body and can sustain repetitive bending, which make it well suited for applications in wearable devices
Ultra-wide bandwidth (UWB) technology is important to improve the performance of antenna in wearable wireless applications due to its merits of high data transmission rate, broad bandwidth, and low-power short-range communication, which is usually realized by fractal and multi-layer structural design [12,13,14]
Summary
Wearable wireless technologies have been attracting increasing attention for solving the conformal problem between wearable antennas and clothes [1,2]. Based on different structural designs, UWB technology has been used in many wearable antenna applications, but the miniaturization of antennas and the improvement of radiation efficiency are still worthy of research [15,16]. Conductive polymers and traditional carbon-based materials have been explored as conductive materials instead of metals to fabricate conformal antennas [32,33,34,35] These materials have good flexibility and are chemically inert, but suffer from mediocre conductivity, which makes it difficult for the antennas to achieve good radiation characteristics in the RF region [36,37]. Due to the above-mentioned limitations of the common materials used for antenna fabrication, most of the proposed wearable antennas exhibit a high profile and poor flexibility, which make it difficult for the antennas to be integrated with on-body devices and to conform to the human body. The performances of the GAF UWB antenna under different wearable application scenarios are presented in Section 4, which is followed by the conclusions
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