RESEARCH ARTICLE A compact dual-band implantable antenna for medical telemetry Kimho Yeap 1 | Chowshen Voon 1 | Takefumi Hiraguri 2 | Humaira Nisar 1 1 Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Kampar, Malaysia 2 Department of Electrical and Electronics Engineering, Nippon Institute of Technology, Miyashiro, Japan Correspondence Kim Ho Yeap, Faculty of Engineering and Green Technology, Universiti Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, Kampar 31900, Perak, Malaysia. Email: yeapkimho@gmail.com Funding information UTAR research fund, Grant/Award Number: IPSR/RMC/UTARRF/2019-C1/Y01 Abstract We present the design of a planar, low-profile dual-band implantable antenna which operates in the 402- to 405-MHz Medical Implant Communication Service (MICS) and the 2.4- to 2.5-GHz Industrial, Scientific, and Medical (ISM) bands. The designed antenna was experimentally validated by implanting it first into a synthetic human skin tissue phantom and then a minced pork model. The measurement results show that the antenna has 10-dB impedance band- widths of at least 120 MHz which covers the MICS band and at least 40 MHz which covers the ISM band. The pro- posed antenna is printed on an RO3210 substrate and it occupies a compact volume of 22 mm × 16 mm × 1.27 mm. The average SAR values at the center frequency of both bands, that is, 403.5 MHz and 2.45 GHz are, respec- tively, below 0.352 and 0.054 μW/kg. Both values are far below the limits stipulated by the IEEE C95.1-1999 (ie, 1.6 W/kg) and IEEE C95.1-2005 (ie, 2 W/kg) standards. The simulated and measured performance of the antenna confirms its good radiation characteristics. KEYWORDS gain, implantable antenna, ISM, MICS, radiation patterns, return loss, SAR 1 | INTRODUCTION The application of implantable medical devices (IMDs) allows biotelemetry and treatments to be administered within the body. The two bands approved for medical implants are the Medical Implant Communication Service (MICS) and Industrial, Scientific, and Medical (ISM) bands. The MICS band ranges from 402 to 405 MHz and is specifically desig- nated for diagnostic and therapeutic purposes, whereas the ISM band which ranges from 2.4 to 2.5 GHz is primarily for microwave heat treating and also for “wake up” applications for energy saving. 1 The key element in an IMD which enables wireless communication between the device and the base station is the antenna. In comparison with conventional antennas which operate in free space, 2–4 the design of an implantable antenna renders certain challenges. Firstly, its geometry has to be compact and small; secondly, the antenna has to be able to operate reasonably well within the lossy human body; thirdly, the design has to comply with the specific absorption rate (SAR) specifications in order to ensure the users’ safety; and, last but not least, the band- width of which has to be sufficiently wide so as to account for frequency detuning caused by varying constitutive parameters in different individuals. Owing to these factors, the design of single band implantable antennas has become a laborious task, let alone, multiband implantable antennas. As can be seen in most literature, the implantable antennas are mostly designed to accommodate only either the MICS 1,5–7 or ISM band. 8–10 In this article, a compact dual-band implantable antenna which operates at both the MICS and ISM bands is pres- ented. The proposed patch antenna is fed by a coplanar waveguide (CPW). Besides exhibiting good impedance and radiation characteristics, we shall demonstrate that the gain and SAR values convincingly indicate that it is suitable to be implanted into human bodies. 2 | DESIGN GEOMETRY AND ANALYSIS The proposed antenna is implanted between the fat and mus- cle layers of a human skin model and is simulated via Ansys HFSS. The parameters of the skin model follow those in Reference 7. Figures 1 and 2 show, respectively, the evolu- tion of the antenna design and the corresponding return losses of the designs. As can be seen from Figure 1A, the fundamental structure of the design originates from the Received: 11 March 2019 DOI: 10.1002/mop.31871 Microw Opt Technol Lett. 2019;1–5. wileyonlinelibrary.com/journal/mop © 2019 Wiley Periodicals, Inc. 1