# A Printed Wearable Dual-Band Antenna for Wireless Power Transfer
## 1 Introduction
The authors also studied the power transfer between a pair of trousers and a shirt and provided three models of resonators attached to fabric on the surface of the clothing. In [20], the authors utilized an RF-based wireless power transfer method to transfer power to medical implanted devices, such as cardiac pacemakers. They designed a novel wideband numerical model (WBNM) for implantable antennas to enable RF-powered leadless pacing. The application of this model and the tissue simulating liquid (TSL) was demonstrated by the design, development, manufacture, and measurement of a novel metamaterial-based conformal antenna at 2.4 GHz. Despite the recent progress in implantable electronic devices, there is still a need for a reliable miniature power source. In [21] the authors studied the optimum frequency for power transfer to implanted devices. They concluded that the optimal frequency is above 1 GHz for small receive coil and typical transmit-receive separations. The author in [22] presented a wireless powering method that overcomes the challenge of miniaturization of the power source by inducing spatially focused and adaptive electromagnetic energy transport via propagating modes in tissue. This method has potential application in a new generation of micro-implants microelectromechanical sensors and logic units. In [23], WPT is used for wearable radio frequency identification (RFID). The authors of [23] illustrated that their proposed wireless transmission structure can operate RFID tags built into smartwatches and claimed that this technology can be adapted to various low-power chips to develop other smart wearable devices, such as smartphones, glasses, and bracelets. In [24], the authors designed a wearable motion sensor on a flexible substrate for mobile health applications. They proposed a compact wireless skin conductance sensor used to monitor the body's emotional regulation process. This flexible substrate can conform to the shape of the user's hand. The major part of any wireless flexible electronic system is the antenna. The antenna has a direct influence on the efficiency of the systems [4]. The size of the antenna is usually the limiting factor in achieving a reasonable power transfer efficiency. Therefore, antennas that can operate at different bands are desirable, since they can reduce the overall size of the system. In [25] we proposed a dual-band antenna and analyzed the bending effects on its performance. The antenna operates at two ultra-high frequency bands (1.6 GHz/3.6 GHz) [25]. The proposed antenna is for wireless power transfer for biomedical applications. This antenna is considered to be printed on a flexible substrate and be implanted inside human body tissue at 10 mm depth. The performance of the antenna under various bending conditions was studied. It was concluded that the proposed antenna respects safety standards to prevent dangerous effects in humans and the antenna's performance remains stable under bending conditions. Following the work in [25], in this paper, we present a flexible antenna, printed on Kapton, with a total dimension of 15 mm \(\times\) 14 mm \(\times\) 0.17 mm, to be integrated with a WPT system. The design, simulation, fabrication, and measurements of the antenna radiation characteristics are presented. A comparison of different types of flexible antennas in the literature and the proposed work in this paper is shown in Table 1.