One of the major challenges in the development of wearable antennas is to design an antenna that can at the same time satisfy technical requirements, be aesthetically acceptable, and be suitable for wearable applications. In this paper, a novel wearable antenna is proposed—textile realization of a slotted waveguide antenna. The antenna is realized using conductive fabric to manufacture the walls of a rectangular waveguide in which the slots were cut out. All connections and cuts are sewn with conductive thread taking over advantages of the traditional process of manufacturing textile objects. The developed slotted waveguide array prototype, containing three slots and designed for operation in the 5.8-GHz ISM band, is experimentally characterized and compared to an equivalent metallic antenna. The achieved operating bandwidth is larger than 300 MHz in both cases. The measured gain of a textile slotted waveguide array is around 9 dBi with a radiation efficiency larger than 50% in the whole operating bandwidth, i.e., the textile array showed a 2 dB lower gain in comparison to the metallic counterpart. The gain is stable in the whole bandwidth and the radiation patterns do not differ. The results demonstrated that such textile antennas are suitable for body-centric communication and sensor systems and can be integrated into clothing, e.g., into a smart safety vest or into a uniform. Further analysis of various realizations of slotted waveguide antennas is presented showing that different versions of the proposed antenna can be used in all three off-body, on-body, and in-body communication scenarios.

The design of wearable antennas presents a challenge from multiple perspectives, as they must meet technical requirements and satisfy safety standards while also being suitable for integration into clothing and aesthetically pleasing. In recent years, the development of conductive fabrics has, in many ways, allowed for significant progress in the manufacturing of wearable antennas, and in previous work, we developed textile slotted waveguide antennas using conductive textiles and traditional sewing processes. However, various aspects of the design and realization of such antennas remain challenging. In particular, this work investigates the issue of using foam-based molds, which enables the realization of thin, flexible, wearable antennas, as well as the issue of antenna feed, specifically the transition from a classic coaxial transmission line to a waveguide. The design of the transition was focused on simplicity and robustness, due to which we limited the number of degrees of freedom in the design process in order to achieve a structure suitable for mounting on textile waveguide antennas. In addition, the antenna design procedure and the body-channel model were considered in order to optimize the performance of the antennas and the wireless body-centric system itself. Several prototypes of different kinds were developed in the 5.8 GHz ISM band, confirming the feasibility of the proposed concepts through experimental results.

Numerous challenges are present in the design and realization of curved leaky-wave metasurface antennas, such as uncontrolled radiation of creeping waves, the requirement for amplitude and phase correction of excited leaky waves, and practical issues related to metallization of complex metasurface patterns on flexible substrates. Therefore, the aim of this paper is to offer a comprehensive methodology for the synthesis of such metasurface antennas on cylindrical substrates, covering analytical tools, design procedure, and fabrication method. As a first step, the theoretical foundation of creeping wave propagation and analytical methodology for extracting their properties on cylindrical metasurfaces is developed. Further, a method for retrieving the optimal metasurface reactance profile is discussed, which is needed to obtain the desired radiation properties from the curved structure. Finally, two cylindrical leaky-wave antenna designs with pencil-beam radiation pattern are developed based on the proposed methodology. The prototypes of the antennas were fabricated using a method called screen-printing, which was essential for realizing the metallization of designed metasurface patterns on flexible low-loss substrate. The antennas are experimentally characterized, and the measured results are compared with theoretical predictions, demonstrating strong agreement and validating the effectiveness of the proposed synthesis approach.