262 IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS, VOL. 25, NO. 4, APRIL 2015 Biotelemetry and Wireless Powering for Leadless Pacemaker Systems Rupam Das and Hyoungsuk Yoo Abstract—In this letter, we address the telemetry and wireless powering problems associated with the recently invented leadless pacemaker. To overcome the telemetry problem, we propose a conformal spiral type Implantable antenna at Medical Implanted Communication Service (MICS) band. In addition, we also apply the recently proposed midfield wireless power transfer (WPT) technique at 1.5 GHz to avoid the bulky energy storage compo- nent. We simulate and experimentally measure the performance of the implantable antenna by using porcine heart tissue. Our research shows that, the implantable antenna and wireless power transfer scheme can be implemented in a leadless pacemaker without any significant coupling between them. Index Terms—Implantable antenna, leadless pacemaker, MICS band, midfield wireless power transfer. I. INTRODUCTION P ACEMAKERS provide electrical stimuli to cause cardiac contractions when intrinsic cardiac activity is inappropri- ately slow or absent. Traditional cardiac pacing or pacemaker systems comprise an implantable pulse generator and lead system. A conventional pulse generator has an interface for connection to and disconnection from the electrode leads that carry signals to and from the heart. The complex connection between connectors and leads provides multiple opportunities for malfunction [1]. Moreover, the pacemaker lead may also interact with magnetic resonance imaging (MRI) systems, which can cause tissue damage. Recently, an MRI-compatible capsule-type leadless pacemaker was introduced to resolve these problems [1], [2]. A leadless pacemaker has several advantages, such as being less invasive (no surgery, more cosmetically pleasing for the patient, i.e., invisible), improved efficiency (no system connections, more readily MRI-compat- ible), and cost-effectiveness (reduced length of hospital stay, less infection or erosion). However, the potential disadvan- tages or technical challenges of the leadless pacemaker cannot be neglected. These challenges include multiple chamber pacing, novel delivery systems, battery longevity, telemetry and long-term efficacy [3]. Manuscript received November 20, 2014; accepted January 16, 2015. Date of publication March 04, 2015; date of current version April 10, 2015. This work was supported by the Basic Science Research Program through the National Re- search Foundation of Korea (NRF) funded by the Ministry of Education, Sci- ence and Technology (2013R1A1A2060266). The authors are with the Department of Biomedical Engineering, School of Electrical Engineering, University of Ulsan, Ulsan, Korea (e-mail: hsyoo@ulsan.ac.kr). Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/LMWC.2015.2400920 The leadless pacemaker's telemetry might facilitate a devel- opment that would allow healthcare professionals to control the device and monitor patients using a standard programmer via smartphones, thereby providing individual treatment to patients in the most rural of areas. Moreover, the leadless pacemaker must remain in place even after the batteries are exhausted. If a noninvasive method of recharging the batteries or powering the leadless pacemaker could be found then this would cease to be a problem and could even be considered an advantage. The implantable antenna allows for wireless monitoring and device control in patients, and the inclusion of wireless power transfer allows for continuous monitoring beyond normal battery life- times. Here, we introduce an implantable antenna [4] which can be incorporated into a capsule-type leadless pacemaker for telemetry. This antenna was designed at Medical Implanted Communication Service (MICS) band ( MHz) [5]. We also utilize the recently published midfield energy transfer technique [6] to check the likeliness of wireless powering of the leadless pacemaker and for removal of batteries. A midfield transmitter antenna was designed for this purpose at 1.5 GHz. Finally, we simulated and measured the performance of both antennas, and we also checked any significant coupling between these two schemes. II. METHODS A. Implantable Antenna Design A spiraled patch PIFA antenna was chosen for the telemetry application. The antenna was designed on a flexible substrate so it can be wrapped around a cylinder-shaped device and can be used in a biotelemetric capsule system for medical purposes. The geometry and dimensions of the proposed an- tenna are shown in Fig. 1. The PIFA antenna can be tuned at about MHz (the MICS band) simply by changing the short-pin positions. If more tuning is required then the width or length of the patch can be varied. A biocompatible and flexible dielectric [7], polyamide ( mm) was used as a substrate as well as a superstrate. Therefore, the total size of the antenna is 20.5 mm 30 mm 0.05 mm (30.75 mm ), which occupies the smallest volume according to the table given in [4]. Then, the antenna was given a capsule or conformal shape, as shown in Fig. 2(b). The Consumer Electronics approved Nanostim leadless pace- maker is smaller than a AAA battery [8]. Generally, a AAA battery has 10.5 mm diameter by 44.5 mm height. 44.5 mm. In our case, the whole conformal antenna has a diameter of 9.46 mm and a length of 20.5 mm, which can fit easily on 1531-1309 © 2015 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.