Miniaturized Dual-Resonant Helix/Spiral Antenna System at MHz-Band for FSK Impulse Radio Intrabody Communications

• Published in: IEEE transactions on antennas and propagation 2020-09, Vol.68 (9), p.6566-6579
• Main Authors: Shi, Jingjing, Liu, Hailian, Wang, Xin, Zhang, Jiayu, Han, Fuye, Tang, Xiaowei, Wang, Jianqing
• Format: Article
• Language: English
• Subjects: Antenna design; Antenna measurements; Antennas; Bandwidth; Coils; Communications systems; Computer simulation; Cylindrical antennas; Diameters; Dissipation factor; Dual-resonant frequency; Electromagnetic fields; Frequencies; Frequency shift keying; frequency shift keying-impulse radio (FSK-IR) system; Helical antennas; helix/spiral-coil antenna structure; Implants; intra-body communication; Keying; Magnetic permeability; MHz band; Miniaturization; Resonant frequencies; Signal to noise ratio; Spiral antennas; Substrates
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2020.2993149

In this article, a miniaturized dual-resonant antenna system at MHz-band operating at around 20 and 50 MHz is proposed for frequency-shift keying impulse radio (FSK-IR) intrabody communications. This antenna system comprises a swallowable helix-coil in-body antenna with a hollow cylindrical shape of 10 mm diameter and 30 mm length, and two single band on-body matched planar spiral-coil antennas with a compact size of 79 mm \times\,\,72 mm \times\,\,2.8 mm. For in-body antenna design, a nonuniform helical pitch structure is utilized to produce dual-resonant frequencies. The soft ferrite magnetic sheet with high relative permeability and low dissipation factor is used as a flexible conformal substrate to realize antenna miniaturization without lumped element loading. Simulation results for antenna performance, electromagnetic field distribution, and specific absorption rate are presented with different tissue-type phantoms, as well as an anatomical numerical human model. In addition, experimental verification of antenna performance and implant transmission characteristics is also conducted in a liquid phantom. At an implant depth of 50 mm, the measured maximum transmission coefficients are −33 and −45 dB at the dual-resonant frequency bands, respectively. Simulation and measurement results demonstrate that the proposed dual-resonant antenna is suitable for the FSK-IR system and can be expected to realize a data rate as high as 10 Mb/s for biomedical implant applications at MHz-band.