Wearable Textile Antenna with a Graphene Sheet or Conductive Fabric Patch for the 2.45 GHz Band

Abstract

Textile patch antennas of simple rectangular, triangular, and circular shape, for operation in the 2.4–2.5 GHz free industrial, scientific, and medical (ISM) band, are designed in this paper. Thirty-six patch antenna prototypes have been fabricated by engaging different patch geometries, patch materials, and substrate materials. Each patch antenna is designed after optimization by a genetic algorithm, which evolves the initial dimensions and feeding position of the prototype’s microstrip counterpart to the final optimal geometrical characteristics of the wearable prototype (with the originally selected shape and materials). The impact of the design and fabrication details on antenna performance were thoroughly investigated. Graphene sheet patches were tested against conductive fabric and copper sheet ones, while denim and felt textile substrates were competing. The comparative study between a large number of different graphene, all, and copper textile prototypes, which revealed the excellent suitability of graphene for wearable applications, is the main contribution of this paper. Additional novelty elements are the compact, flexible, and easy-to-fabricate structure of the proposed antennas, as well as the use of state-of-the-art conductive materials and commercially available fabrics and the extensive investigation of many prototypes in various bending conditions. Simulations and measurements of the proposed antennas are in very good agreement. All fabricated prototypes are characterized by flexibility, light weight, mechanical stability, resistance to shock, bending and vibrations, unhindered integration to clothes, low-cost implementation, simple, time-saving, and industry-compatible fabrication process, and low specific absorption rate (SAR) values (computed using rectangular and voxel models); the graphene prototypes are additionally resistant to corrosion, and the circular ones have very good performance under bending conditions. Many antenna prototypes demonstrate interesting characteristics, such as relatively wide bandwidth, adequate gain, firm radiation patterns, coverage of the ISM band even under bending, and very low SAR values. For example, the circular graphene patch (with 55.3 mm diameter attached upon a 165.9 × 165.9 mm) felt substrate CGsF1 prototype accomplishes 109 MHz measured bandwidth, 5.45 dBi gain, 56% efficiency, full coverage of the ISM band under bending, and SAR less than 0.003 W/Kg.

The Influence of Textile Substrates on the Performance of Textronic RFID Transponders

“…In this frequency range, the problem of the variability of the substrate parameters can be considered as quasi-stationary for a given textile. The problem may arise when the broader band of frequency is to be analyzed as well as when new composite material is considered [ 13 , 18 , 37 , 38 ].…”

“…Typically, these antennas are made by combining (a) classic conductive materials with a textile base (e.g., copper foil or screen-printed layer on cotton [ 14 ] and other substrates [ 15 ]) or (b) innovative conductive textile materials (e.g., conductive polymers, electrotextiles, graphene sheet, fabrics with metal threads [ 16 , 17 ]) with classic textiles (e.g., graphene sheet with denim or felt [ 13 , 18 ]). In addition, the integration of a typical flexible antenna (e.g., made on polyethylene terephthalate PET foils) with fabrics is frequently used [ 18 , 19 ]. The latest solutions are related to the increasing availability of numerically controlled machines and new materials.…”

Dual-Band CPW Graphene Antenna for Smart Cities and IoT Applications

“…The proposed antenna is configured by a coplanar waveguide line to feed the antenna with a characteristic impedance Z 0 . In addition, the antenna has two radiator patches with an isosceles trapezoidal form [ 30 , 31 , 32 , 33 ]; Figure 1 shows the geometry of the proposed antenna. In this geometry, w 4 controls the lowest frequency band ( f min ), and w 2 works over the higher frequency band ( f min ).…”

“…Moreover, Lamminen et al [ 27 ] shows a printed dipole antenna in Dupon dielectric and graphene flakes for ISM bands. An important application of graphene antennas is wearable technology [ 28 , 29 , 30 ]; Zu et al [ 28 ] presented a design over a flexible substrate and highly conductive graphene film, and Sindhu et al [ 29 ] employed laser-induced graphene (LIG) to print the design; both antennas operate at 5.8 GHz. Kapetanakis et al [ 30 ] presented wearable patch antennas with graphene over a textile substrate at 2.45 GHz.…”

Negative Index Metamaterial-Based Frequency-Reconfigurable Textile CPW Antenna for Microwave Imaging of Breast Cancer

“…Work carried out over the past decade have employed ultrawideband (UWB) antenna technology, with its unique features of high-speed data rates, very small signal interference, simple low-cost design, to construct microwave imaging systems [5]. Existing work [9,10] have also explored the use of flexible materials to design the antennas and, thus, it will be suitable for on-body applications. In addition, previous studies demonstrated that incorporating metamaterials (MTMs) into conventional antenna design resulted in enhancement of antenna's gain bandwidth, higher radiation efficiency, improvement in radiation pattern, and reduction of specific absorption rate (SAR) [8,11,12].…”