Implantable antenna gain enhancement using liquid metal-based reflector
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Implantable antenna gain enhancement using liquid metal‑based reflector Soumyadeep Das1 · Debasis Mitra1 · Bappaditya Mandal2 · Robin Augustine2 Received: 23 April 2020 / Accepted: 28 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This article presents gain enhancement methodology for a dual-ring slot antenna using a frequency selective surface (FSS) as reflector. The FSS structure is formed with liquid metal placed inside the microfluidic channels created on the surface of the polydimethylsiloxane. Non-toxic liquid metal galinstain has been used to ensure biocompatibility. The FSS structure is placed below the ring slot antenna to reflect the back radiation, which in turn enhances the antenna directivity. Subsequently, the antenna gain has been increased as well. A fabricated prototype of the antenna-FSS system, operating at 2.45 GHz, has been analysed both inside human tissue mimicking fluid and pork slab to validate the simulation results. The inclusion of the liquid metal-based reflector increases antenna gain by almost 4 dB as well as ensures required biocompatibility and flexibility. Also the specific absorption rate of the antenna is observed to be reduced. Keywords Biomedical application · FSS reflector · Gain enhancement · Implantable antenna · Liquid metal
1 Introduction Biomedical telemetry system essentially refers to the extraction of the physiological data from human body and also the monitoring of the concerned patient [1]. Wireless biotelemetry has been gaining significant consideration over the last 2 decades due to the mobility and flexibility it offers in modern day health care industry [2]. Previously, the implantable medical devices (IMD) used low-frequency inductive links for communication [3], resulting in high data loss, limited communication range, and increased sensitivity of the inductive coils [4]. To overcome these drawbacks, at present, IMDs are made to communicate in radio frequency (RF) band. Both the medical implant communications service (MICS) band and industrial, scientific, and medical (ISM)
* Soumyadeep Das [email protected] 1
Department of Electronics and Telecommunication Engineering, Indian Institute of Engineering Science and Technology, Shibpur, Howrah 711103, West Bengal, India
Microwaves in Medical Engineering Group, Division of Solid‑State Electronics, Department of Electrical Engineering, Ångström Laboratory, Uppsala University, Uppsala, Sweden
2
band have been allotted for medical communication purpose by international regulatory bodies (FCC, ITU, IEEE, etc.) [5]. Implantable antennas are being designed as transceiver unit for the IMDs to communicate the physiological data with other monitoring devices placed outside the patient’s body using RF band transmission [6]. Over the years, multiple IMDs have been designed, such as, implantable cardioverter defibrillator and loop recorder [7], deep brain stimulators, bladder stimulators and diaphragmatic pacemakers [8]. As the transceiver unit of the IMDs,
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