## 1 Introduction
Various technologies and new materials have been developed that enable us to make biodegradable and heterogeneously layered materials to support various microsystem and sensors. While these stretchable, flexible, and integrated biodegradable sensors are remarkable, the cost and requirements might not be feasible for everyday wearable devices. When it is possible to combine a rigid miniaturized antenna with wearable sensors, a more cost-effective and feasible solution might be provided. Wearable sensor antennas should be analyzed in real-world situations, including the existence of the human body, bending and wrinkling of clothing, and washing. The buttons are a good candidate for antennas to be integrated to. They can be easily mounted on textiles materials. Buttons are made of rigid material, which helps in stabilizing the performance of the antenna. Rigid conductors, such as copper, can be used in BSA design. The use of highly conductive metallic vs. e-textile materials that usually have lower conductivity improves the performance of the antenna. Further, the BSA design can be easily integrated into clothes at various positions. While the rigidity of the buttons is an advantage, it is not always possible. The unique design we propose can either be in a button shape or it can be worn using a wristband [24; 25]. Our goal was to design a BSA for WBAN applications that would meet the following requirements: (1) multi-band operation for various WBAN bands; (2) small size in the shape of a button to increase the wearer's comfort (a small rigid PCB size, with an electronic system that could be integrated into a wristband or a jacket's button); (3) high stability in resonance frequency, impedance matching, and omnidirectional radiation pattern; and (4) good communication range. These properties were not found to be simultaneously satisfied by small sensor antennas proposed in the published literature. The advantage of the proposed BSA is that it does not require special fabrication technology and the material and components are easily available. Further, our proposed BSA is easy to maintain and replace. The standalone unit can be simply detached and replaced, as inspired by [26; 27]. In our proposed design, an asymmetrical small-sized rigid PCB is employed as the button, with a flexible conducting textile (clothing) acting as the ground plane while a rigid coaxial feed line is used to feed to a circular sensor module. This BSA provides a small form factor and can easily be integrated into a hand-watch cover. This topology ensures robustness and minimum effects due to bending and stretching. To the best of our knowledge, this is the first time a thorough investigation of a new button sensor antenna system design, and its performance is presented. We propose a complete wireless sensor system that incorporates the newly designed antenna with the transceiver system comprising chips and lumped elements and is equipped to communicate with a WiFi router. This compact sensor is compatible with the IEEE 802.11b/g/n routers. The paper is arranged as follows: After a brief introduction, Section 2 explains the design requirements and procedure of the wearable button sensor antenna. The measurement results are provided in Section 3. Section 4 concludes the paper with recommendations for future work.