An antenna design concept with detachable radiation elements offering modular geometry reconfigurabilities for wearable applications is presented. By utilizing snap-on buttons, both as the radio-frequency (RF) connection and mechanical holding mechanism, different modularly interchangeable microstrip patches are employed to demonstrate geometry reconfigurabilities in terms of polarization and resonance frequency. The uniqueness of the design arises from the fact that all configurations share one common feed structure which consists of a two-layered substrate including snap-on buttons, a ground plane, and a proximity coupled feed. To show the concept, modular realizations with different functionalities in terms of polarization or resonance frequency are demonstrated in this paper. First, a detachable patch offering interchangeable right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) at 5 GHz is proposed. Second, a demonstration of a planar inverted-F antenna (PIFA) concept offering interchangeable resonance frequencies for the 2.4- and 5.3-GHz bands of wireless local area networks (WLAN) is given. Finally, a patch module designed for 8-GHz operation is presented to show the versatility in frequency modularity. Experimental results of the fabricated antennas in freeAn antenna design concept with detachable radiation elements offering modular geometry reconfigurabilities for wearable applications is presented. By utilizing snap-on buttons, both as the radio-frequency (RF) connection and mechanical holding mechanism, different modularly interchangeable microstrip patches are employed to demonstrate geometry reconfigurabilities in terms of polarization and resonance frequency. The uniqueness of the design arises from the fact that all configurations share one common feed structure which consists of a two-layered substrate including snap-on buttons, a ground plane, and a proximity coupled feed. To show the concept, modular realizations with different functionalities in terms of polarization or resonance frequency are demonstrated in this paper. First, a detachable patch offering interchangeable right-hand circular polarization (RHCP) and left-hand circular polarization (LHCP) at 5 GHz is proposed. Second, a demonstration of a planar inverted-F antenna (PIFA) concept offering interchangeable resonance frequencies for the 2.4- and 5.3-GHz bands of wireless local area networks (WLAN) is given. Finally, a patch module designed for 8-GHz operation is presented to show the versatility in frequency modularity. Experimental results of the fabricated antennas in free space, worn by a torso phantom and in bending conditions, validate the concept and prove that this type of modular design offers convenient, passive, low cost, and versatile system reconfigurabilities, which can benefit wearable applications. space, worn by a torso phantom and in bending conditions, validate the concept and prove that this type of modular design offers convenient, passive, low cost, and versatile system reconfigurabilities, which can benefit wearable applications.

A robust solution to realize reconfigurable textile antennas for wearable applications is proposed. The main idea is to integrate active components (such as varactors or PIN diodes) and their biasing circuit into a compact arrangement of back-to-back commercial snap-on buttons. The resulting module can provide versatile reconfigurabilities for textile antennas, with secure protection for the rigid electronics while maintaining stable and repeatable electrical connection to the flexible metalized textiles. To demonstrate the concept, a dual-band frequency-reconfigurable wearable textile patch antenna with a dedicated varactor-loaded module is designed, fabricated and experimentally characterized. A good agreement observed between simulation and measurement results validates the concept of the reconfiguration module. The antenna exhibits tuning ranges of 32.8% and 8.8% for its two operation bands designed to include the 2.45 and 5.8 GHz industrial, scientific and medical (ISM) radio bands, respectively. In addition, the antenna possesses mechanically secure and reproducible electronics-to-textile connections as observed during the measurement campaign. These findings indicate that the proposed snap-on button concept is a promising practical engineering solution for reconfigurable textile antennas.

This letter proposes a wearable dual-band dual-mode button antenna for wireless body-area network applications. It covers the 2.45 and 5.8 GHz Industrial, Scientific, and Medical bands. The two operating modes of the antenna are designed to share a common radiator with different functionalities for distinctive communication requirements. The antenna operates from 2.32 to 2.57 GHz as a top-loaded monopole antenna with linear polarization, which is applicable for on-body communications due to its omnidirectional radiation pattern. In contrast, it works as a crossed-dipole antenna in its higher operation band extending from 5.72 to 7.85 GHz, in which it exhibits broadside radiation with circular polarization suitable for off-body communications. The experimental characterization on the fabricated antenna prototype, both in free space and proximity to the human body, proves that the antenna operates as anticipated with dual-band and dual-polarization characteristics for wearable applications.

We demonstrate a concept of compact and highly efficient circular traveling wave series-fed microstrip patch array working at 10 GHz. The patch elements are excited by a microstrip line through coplanar proximity coupling. A dual-port feeding allows us to select the direction of the traveling waves and, consequently, the sense of circular polarization of the patches. Simultaneous feeding to both ports with proper amplitude and phase difference can result in radiated waves of arbitrary polarization. Owing to the circular array arrangement and the strong proximity coupling, the antenna exhibits a compact structure and achieves a high antenna efficiency of 90% with seven patches. Based on reciprocity, the antenna can readily be also utilized for polarimetry applications for which the signal amplitude at each port is proportional to the amplitude of each individual sense of polarization. Measured results of an antenna prototype successfully validate the concept.

A reconfigurable wearable textile antenna with wide frequency tuning range is demonstrated in this work. Frequency agility is realized by adding a coplanar reconfiguration module to a planar inverted-F antenna (PIFA) constructed in textile technology. The reconfiguration module consists of a small flexible printed circuit board (PCB) which integrates a tuning circuitry with commercial snap-on buttons as electronic-to-textile connectors. Using this module equipped with a varactor diode, the frequency reconfigurability of the PIFA is investigated and optimized parametrically for maximum tuning range, exploiting a smooth transition from a quarter-wave to a half-wave patch resonant mode. A fabricated prototype demonstrates a very wide tuning range of approximately 70% (or one octave) with stable directive radiation characteristics, as predicted by simulations. The robust performance and mechanical stability of the reconfigurable antenna in various on-body and bending configurations validates the viability of the antenna tuning concept and the practicality of the proposed coplanar reconfiguration module.

A flexible dual-band dual-mode wearable antenna with a hybrid dielectric substrate is proposed for off- and on-body communications. It operates at two Industrial, Scientific, and Medical (ISM) bands, namely with a broadside radiation at 2.45 GHz and an omnidirectional radiation pattern at 5.8 GHz. A hybrid substrate based on flexible polydimethylsiloxane (PDMS) and PF4-foam materials is introduced to overcome the low radiation efficiency in both modes due to the PDMS substrate. The hybrid substrate is realized by replacing the PDMS substrate areas exhibiting high power loss density with a low-loss PF4-foam material. This reduces the dielectric loss and improves the radiation efficiency by an average value of 17% and 20% in the 2.45 and 5.8 GHz ISM bands, respectively. Such a technique extracts the desirable properties of two dielectric materials and combines them to achieve improved antenna performance. The common properties of both materials include high flexibility, resilience, water resistance, and robustness. Importantly, the hybrid substrate offers an optimal trade-off between antenna size and radiation efficiency. In comparison to a PF4-foam-only counterpart, the proposed hybrid substrate demonstrates an antenna area reduction of 19%, while the PDMS-only substrate design exhibits an antenna area reduction of 37%. Additionally, the design methodology of the dual-mode antennas allows for independent control of the resonances, providing a high degree of design flexibility.