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A novel wearable substrate integrated waveguide antenna fabricated entirely from textile materials is presented. The cavity-backed slot antenna operates in the 2.45 GHz industrial, scientific and medical band, for short range communication between rescue workers. A prototype of the antenna was fabricated and tested: good performance was obtained in terms of input matching and radiation pattern. Moreover, measurements performed on the antenna after bending and integration into clothing indicate high robustness against deformation and low influence of the human body on antenna performance, making the design well-suited for on-body use.Introduction: The design of wearable components and antennas for wireless applications received significant attention [1] in the past decade. In particular, localization and tracking of fire-fighters in rescue operations, as well as communication in critical conditions, require lowcost and efficient systems that are comfortable to wear. Therefore, components and systems should be low-profile, light-weight and mechanically flexible, and the adopted substrates need to be flame resistant and water repellent. The textile fabrics typically applied in firefighter garments represent good candidates for implementing antennas that are suitable for integration into protective garments. A variety of patch antennas on textile, operating in the 2.4-2.4835 GHz industrial, scientific and medical (ISM) band, were proposed [1]. These antennas require a sufficiently large ground plane to limit the influence of the human body on the antenna's radiation characteristics. In addition, antenna performance should remain stable when the textile patch is subjected to bending [2]. In this Letter, a textile cavity-backed slot antenna in substrate integrated waveguide (SIW) technology is presented. To the authors' best knowledge this is the first implementation of a microwave SIW structure with textile materials. Cavity-backed antennas offer several advantages, such as suppression of unwanted surface waves and lower sensitivity for on-body operation, as well as a high front-to-back ratio [3]. SIW technology was chosen as a simple cost-effective fabrication process, which is already well-developed for printed circuit boards [4]. Furthermore, it allows easy integration of passive and active components onto the antenna [5], thus permitting the realization of complete systems on a textile carrier. An SIW cavity-backed slot antenna in textile materials was designed, fabricated and experimentally verified. The structure exhibits compact size and good flexibility, thanks to the use of eyelets as metalized holes implementing the SIW cavity. On-body measurements were performed, and the effect of bending was investigated to evaluate the antenna performance under realistic operating conditions.

Abstract-Although Substrate Integrated Waveguide (SIW) technology is well-established for the fabrication of microwave circuits on rigid printed circuit boards, and the first implementations of textile SIW antennas have recently appeared in literature, up to now, no complete set of SIW microwave components has been presented. Therefore, this paper describes the design, manufacturing, and testing of a new class of textile microwave components for wearable applications, implemented in SIW technology. After characterizing the adopted textile fabrics material in terms of electrical properties, it is shown that folded textile SIW components, such as interconnections, filters and antennas form excellent building blocks for wearable microwave circuits, given their low profile, flexibility and stable characteristics under bending and in proximity of the human body. Hence, they allow the full exploitation of the large area garments offered for the deployment of wearable electronics. Besides SIW interconnections, a folded textile SIW filter operating at 2.45 GHz is designed and tested. The filter combines excellent performance in the band of interest with good out-ofband rejection, even when accounting for the tolerances in the fabrication process. Finally, a folded SIW cavity-backed patch antenna is fabricated and experimentally verified in realistic operating conditions. Index Terms-Cavity-backed antenna, folded waveguide, substrate integrated waveguide, textile material, wearable systems.

A novel substrate integrated coaxial line (SICL) is presented and experimentally verified in this paper. This structure exhibits unimodal operation over a wide frequency band, is shielded and not dispersive, can be fabricated by using simple, low-cost thin-film process, and can be easily integrated with active devices. Moreover, the same technology results particularly suitable to realize passive components for wideband applications. The design of a Lange coupler with operation bandwidth of 66%, to be used in a Multi-port Impulse Radio for Ultra Wide Band applications, is reported.Index Terms-Hybrid coupler, substrate integrated circuits, ultra wide band.

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