Research Article An Approach to Improve the Misalignment and Wireless Power Transfer into Biomedical Implants Using Meandered Wearable Loop Antenna Muayad Kod , 1 Jiafeng Zhou , 2 Yi Huang , 2 Muaad Hussein , 3 Abed P. Sohrab , 4 and Chaoyun Song 5 1 Electrical and Electronics Engineering, University of Kerbala, Kerbala, Iraq 2 Electrical Engineering and Electronics, e University of Liverpool, Liverpool, UK 3 Electrical Power Techniques Engineering, Southern Technical University, Basrah, Iraq 4 James Watt School of Engineering, University of Glasgow, Glasgow, UK 5 School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh, UK Correspondence should be addressed to Jiafeng Zhou; jiafeng.zhou@liverpool.ac.uk Received 27 August 2020; Accepted 2 February 2021; Published 20 February 2021 Academic Editor: Alex Takacs Copyright © 2021 Muayad Kod et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. An approach to improve wireless power transfer (WPT) to implantable medical devices using loop antennas is presented. e antenna exhibits strong magnetic ﬁeld and dense ﬂux line distribution along two orthogonal axes by insetting the port inside the antenna area. is design shows excellent performance against misalignment in the y-direction and higher WPTas compared with a traditional square loop antenna. Two antennas were optimized based on this approach, one wearable and the other implantable. Both antennas work at both the ISM (Industrial, Scientiﬁc, and Medical) band of 433 MHz for WPT and the MedRadio (Medical Device Radiocommunications Service) band of 401–406MHz for communications. To test the WPT for implantable medical devices, a miniaturized rectiﬁer with a size of 10 mm × 5 mm was designed to integrate with the antenna to form an implantable rectenna.epowerdeliveredtoaloadof4.7kΩ canbeupto1150 μWwhen230mWpoweristransmittedwhichisstillunderthe safety limit. is design can be used to directly power a pacemaker, a nerve stimulation device, or a glucose measurement system which requires 70 μW, 100 μW, and 48 μW DC power, respectively. 1. Introduction Wireless power transfer (WPT) to implantable devices has attracted signiﬁcant attention in the last decade. It is a promising choice for delivering power to the implants which may avoid the surgery required to replace batteries [1]. is power transfer takes place when a voltage is induced at a receiver due to electric and magnetic ﬁelds generated by an external transmitter [2]. Traditionally, two major techniques of delivering power wirelessly into the implant exist. e ﬁrst one is far-ﬁeld transmission using antennas [3–9]. An external antenna is placed away from the body to power and communicate with implants through an implantable antenna. is approach re- stricts the patient’s mobility and exposes the whole body to the radiated power. e second technique is the inductive coupling between two coils [10–19]. ese coils should be kept aligned well; otherwise, the strong electromagnetic coupling will be lost. Inductive coupling is not restricted to coils. Antennas can be used in power transmission based on this technique if it is placed in close proximity within the near-ﬁeld region. ese antennas are wearable on the body and used to wirelessly charge as well as communicate with implants. Loop antennas are widely used for this purpose in the literature because of the high magnetic ﬁeld in the near-ﬁeld region. A pair of square loop antennas was used to characterize the eﬀect of the human head on the transmission of RF signal at the MedRadio band in [20]. Another pair of circular loop and triangle patch antennas was used to improve communications with implants in [21]. In [22], a near-ﬁeld wireless power link was established between a brain implantable Hindawi Wireless Power Transfer Volume 2021, Article ID 6621899, 12 pages https://doi.org/10.1155/2021/6621899