1558-1748 (c) 2019 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. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/JSEN.2019.2924948, IEEE Sensors Journal Abstract—The brain-machine interface (BMI) is a new area of research and it is still in the development stage. The key component for the brain-machine interface is internal and external antennas. In this paper, we propose an implantable antenna for wireless brain signal sensing and monitoring using an inhomogeneous multi-layer model of the human head. A model with seven layers composed of skin, bone, fat, dura, cerebro spinal fluid (CSF), grey matter and white matter was adopted for our multi-layer model. The antenna was embedded below the bone and above the dura of the head phantom. Artificial tissue emulating (ATE) materials were fabricated in semi-solid form and measurement was carried out to check the permittivity and loss tangent of each semi-solid ATE. Implanted antennas for wireless brain signal monitoring data must be compact, lightweight and biocompatible. The proposed antenna was designed with Taconic RF-35 as the substrate with an overall size of 10 mm x 10 mm x 0.5 mm 3 . The proposed antenna has a -10 dB reflection bandwidth of 2.42-2.50 GHz and a gain of -25 dBi at the broadside direction. The top and bottom insulators with a thickness of 0.5 mm each were also designed with a Taconic RF-35 substrate. A good agreement between simulated and measured results was achieved for the proposed antenna for both in free space and inside of head phantom. Index Terms—Brain-machine interface (BMI), implantable antenna, gain, artificial tissue emulating (ATE), cerebro spinal fluid (CSF). I. INTRODUCTION HE recently developed brain–machine interface (BMI) is an emerging and promising area that is expected to restore functionalities to paralyzed individuals [1-2]. Research on the BMI has received extensive attention since the first experiment verified that electrical activity generated by ensembles of cortical neurons can be employed directly to control a robotic manipulator [3]. The BMI consists of several parts: sensors for neural recording, signal processing IC, a program for brain simulations, a wireless link to connect with an external unit and real time brain mapping to effectively track and decode the neural activities [2]. Reliable BMI systems are still in the development stage. Neural recording systems need to be very This work was partly supported by Institute of Information & communications Technology Planning & Evaluation (IITP) grant funded by the Korea government(MSIT) (No. 2017-0-00659) and Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (No. 2018R1D1A1B07049984). The associate editor miniaturized, biocompatible, wirelessly powered and able to flow data directionally. It is the most promising and demanding task to extract the brain signal data from the implanted systems. [4-10]. In [2], the authors used short-range RFID backscattering technology to communicate with the neural recording unit. The antenna for such a system is extremely challenging. The compact antennas surrounded by biological tissues have different characteristics and different head implantable antennas have been proposed in the recent past [11-25]. In [26], authors proposed a microwave signal generation system for brain stimulation. Fig. 1. Overview of brain machine interface. It is important to note that none of the earlier head implantable antennas were measured with a tissue model with seven layers, which makes the former results less realistic than our proposed antenna. Moreover, the proposed antenna in the human brain phantom has a broadside radiation pattern, which is a unique feature of this proposed antenna. In this study, we used a 2.42-2.50 GHz frequency band for establishing wireless power and establishing a connection with a miniaturized neural recording unit. There is an implantable antenna within neural recording unit which transfers power and data to an external antenna. In this paper we propose a novel patch type implantable antenna for the brain-machine interface. We simulated the antenna in a multi-layer tissue model of a coordinating the review of this paper and approving it for publication was Prof. Pai-Yen Chen. (Corresponding author: Jae-Young Chung.) The authors are with the Department of Electrical and Information Engineering, Seoul Nat’l Univ. of Science and Technology, Seoul 01811, South Korea (e-mail: jychung@seoultech.ac.kr). An Implantable Antenna with Broadside Radiation for a Brain-Machine Interface Biswarup Rana, Jae-Yeon Shim, Jae-Young Chung, Senior Member, IEEE T