Research On Implantable In-Body Antennas For MHealth Applications

With the development of economy and the improvement of people’s health consciousness, mobile-Health(mHealth) technique has attracted wide attention of the whole society. The development of mHealth technique has prompted the emergence of implantable medical devices. Those devices not only can help doctors measure and obtain physiological information for disease prevention, diagnosis and treatment in real-time, but also can provide more comfortable treatment services for patients. In order to obtain the physiological information that gathered by implantable devices and send treatment signals to implantable devices, wireless communication is essential. As the key component for wireless communication between intra-body medical devices and external devices, implantable antennas will affect the transmission of biomedical signals. Excellent performance of implantable antennas may improve the safety and reliability of the whole mHealth system. Therefore, research on implantable antennas is significant and valuable.This work was supported in part by the National Natural Science Foundation of China under Grant 61372008, and in part by the Science and Technology Planning Project of Guangdong Province under Grant 2014A010103014, 2015B010101006, and investigates implantable antennas for biomedical applications. The content mainly includes as follows:1) By employing substrate with high dielectric constant and stacked PIFA structure,a compact implantable antenna for biomedical application in medical implant communication services band(MICS band: 402-405 MHz) is proposed. Through parameter optimization,the proposed antenna achieves miniaturization with a dimension of 80.75 mm3 and the impedance bandwidth is 391-417 MHz(6.5%) with a peak gain of-38.6 dBi. The results show that reliable communication can be guaranteed. Furthermore, the specific absorption rate(SAR) distribution is evaluated for safety concerns.2) Due to the complexity and dispersion of human tissues, wide bandwidth is required in case of frequency shift. As the bandwidth of the above-mentioned implantable antenna is narrow and in order to improve the robustness of wireless communication, the antenna with bandwidth enhancement in MICS band is presented. And it realizes wideband with a bandwidth of 360-550 MHz(47%)by short pin loading to increase resonance point. The performance of the proposed antenna under different implanted conditions reveals that high reliability can be obtained.3) Due to the special advantage of circular polarization(CP) implantable antennas for wireless communication between implantable devices and external devices, a single-fed miniaturized wide-beamwidth circularly polarized implantable antenna, which operating in the industrial, scientific and medical(ISM) band(2.40-2.48 GHz), is presented and experimentally verified for biomedical applications. The proposed antenna achieves miniaturization with a dimension of 8.5 × 8.5 × 1.27 mm3 by employing four C-shaped slots and a complementary split-ring resonator(CSRR). Meanwhile, by adjusting the split of CSRR, circular polarization is realized. Furthermore, the effect of biocompatibility approaches is discussed and the link margin is analyzed. And finally, the proposed antenna is fabricated and measured. The measured results agree well with simulated results, validating the theoretical design.