TECHNICAL PAPER RF rectiﬁers for EM power harvesting in a Deep Brain Stimulating device Md. Kamal Hosain • Abbas Z. Kouzani • Susannah Tye • Akif Kaynak • Michael Berk Received: 1 July 2014 / Accepted: 6 January 2015 Ó Australasian College of Physical Scientists and Engineers in Medicine 2015 Abstract A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectiﬁer, to harvest energy from electromagnetic ﬁelds for its operation. This paper presents optimization of radio fre- quency rectiﬁer circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efﬁciency, and high output voltage rectiﬁer. Four different rectiﬁers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadru- pler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simu- lation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectiﬁers. The performance of the fabricated rectiﬁers is evaluated using a 915 MHz radio frequency (RF) energy source. The maxi- mum measured conversion efﬁciency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectiﬁers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5–15 kX. The conversion efﬁciency of the rectiﬁers decreases signiﬁcantly with the increase in the input power level. The Delon doubler rectiﬁer provides the highest efﬁciency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectiﬁer gives the lowest efﬁciency for the same inputs. By considering both efﬁciency and DC output voltage, the charge pump rectiﬁer outperforms the other three rectiﬁers. Accordingly, the optimised 2-stage charge pumped rectiﬁer is used toge- ther with an antenna to harvest energy in our DBS device. Keywords RF  Rectiﬁer  Deep brain stimulation  Energy harvesting  Passive device Introduction DBS is used for treatment of a range of neurological and psychiatric disorders. Preclinical research involving labora- tory animals is needed to study the principles of DBS and the pathophysiological mechanisms whereby its treatment effects are facilitated [1]. Different types of DBS devices exist that are used in preclinical studies on laboratory animals. Most of the existing devices employ sophisticated circuitry, and are therefore large in size. In recent years, several miniature head- mountable devices have been reported in the literature [2]. The head-mountable devices can be classiﬁed as active or passive; the active devices are operated by a battery whereas the pas- sive devices are operated by an energy harvester [3]. Most of the existing head-mountable devices are active, hence they face issues such as large battery size, large battery weight, battery replacement, and so on [4]. Thus, a consequent requirement is to substitute the battery in a DBS device with an energy harvester. Energy can be harvested from different energy sources including solar, vibration, temperature gradient, electromag- netic (EM) ﬁelds [5]. The EM energy can be harvested from ambient sources or a feeding source [6]. Since the energy Md. K. Hosain (&)  A. Z. Kouzani  A. Kaynak School of Engineering, Deakin University, Waurn Ponds, Geelong, VIC 3216, Australia e-mail: mhosain@deakin.edu.au S. Tye Department of Psychiatry and Psychology, Mayo Clinic, Rochester, MN 55905, USA M. Berk School of Medicine, IMPACT Strategic Research Centre, Deakin University, Waurn Ponds, Geelong, VIC 3216, Australia 123 Australas Phys Eng Sci Med DOI 10.1007/s13246-015-0328-7