Miniaturized Antenna for High Data Rate Implantable Brain-Machine Interfaces

Abstract

Technological advancements in medical care have necessitated the development of efficient and miniaturized implantable medical devices. This paper presents an ultra-wide-band implantable antenna for use in scalp-based biomedical applications covering the industrial, scientific, and medical (ISM) (2.4−2.48 GHz) band. The proposed antenna is mounted on a 0.1−mm thick liquid crystalline polymer (LCP) Roger ULTRALAM (tanδ = 0.0025 and ε r = 2.9), serving as a dielectric material for both the superstrate and substrate layers. LCP materials are widely used in manufacturing electronic devices owing to their desirable properties, including flexibility, conformable structure, and biocompatibility. To preserve the capability of an electrically small radiator and achieve optimum performance, the proposed antenna is designed to have a volume of 9.8 mm 3 (7 mm ×7 mm × 0.2 mm). The addition of a shorting pin and open-ended slots in the radiating patch, and close-ended slots in the ground plane facilitates antenna miniaturization, impedance matching, and bandwidth expansion. Notably, the antenna exhibits a peak gain of −20.71 dBi and impedance-matched bandwidth of 1038.7 MHz in the ISM band. Moreover, the antenna is safe to use according to the IEEE C905.1-2005 safety guidelines based on low specific absorption rates. To evaluate the performance of the implantable antenna, finite-element simulation was performed in homogeneous and heterogeneous environments. For validation, measurements were performed in a minced pork-filled container. The simulation results are consistent with the measurements. In addition, a link budget analysis is performed to confirm the robustness and reliability of the wireless telemetric link and determine the range of the implantable antenna. INDEX TERMSImplantable antenna, high gain, novel shaped, specific absorption rate, ultra-wide band. Several frequency bands are regulated by the Federal Communications Commission (FCC) for use in biomedical applications, including medical implant communications service (MICS, 402−405 MHz), improved MICS, called the medical device radio communication Service (MedRadio, 401−406 MHz) [11], and industrial, scientific, and medical (ISM, 433−438 MHz; 902−928 MHz; 2.4−2.48 GHz; and 5.725−5.875 GHz) bands. To extend the device lifetime and battery energy, a sleep-wakeup mode is utilized at 2.45 GHz VOLUME 4, 2016

Electrically-Small Antenna With Low SAR for Scalp and Deep Tissue Biomedical Devices

“…Table 3 presents the detailed SAR values of the proposed antenna, including the allowed maximum power. These values are much less than existing implantable antennas [10], [16], [18]- [23].…”

“…The antenna, however, has a bulky volume of 57 mm 3 and 48.98 mm 3 in the flat and wrapped form, respectively. Likewise, in [16], an ultra-wideband scalp implantable antenna operating at ISM (2,400-2,480 MHz) band is proposed. The proposed antenna offers a bandwidth of 1,038.7 MHz and a peak gain of -20.71 dBi with a volume of 9.8 mm 3 .…”