Minimization of the RF link loss of a neuropotential recording system using metamaterial based antennas

Abstract

In this thesis, a novel method of performance enhancement for efficient biopotential sensing between antenna pairs has been presented, exploiting the concepts of superstrates and metamaterials. The superstrate and the antenna ground form a Fabry-Perot resonant cavity, and the inclusion of dielectric materials in-between the antenna patch and the superstate are expected to enhance transmissions well as resulting in a miniaturized structure. The ideas are tested on two simulation environments; first the two antennas are placed in free space, and later one antenna is buried inside a frequency dispersive tissue whose characteristics are like different biological tissues. For the case when the two antennas are buried in free space, a gain improvement of around 5dB is noted, when the two antennas are separated in free space, and when the antennas are separated by a biological medium, the improvement is found around 8dB. A proof-of-concept biosensing system with practical materials and frequency dispersive biological tissue is presented afterwards. For the design, the final transmission loss is found to be -14.1 dB in HFSS, and -12.33 dB in CST, both fair very well with the performance of the biosensing systems in the existing literature. However, the proposed concept also appears to be much less sensitive to misalignment between the two antennas, and the simulation results showed that the transmission degrade by less than 2.5 dB, for 1 cm of misalignment. The safety measurements of specific absorption rate meet the desired requirements of patient safety and suggest that this method can be used for long term biosensing, and the proposed idea is also found to work in multiple frequencies. Finally, a specific application of neuropotiential has been addressed. An antenna pair system with practical human head materials is designed, which shows a transmission loss of 11.27 dB (HFSS) and 10.5 dB (CST) at a design frequency of 4.8 GHz. And a demonstration of signal extraction has been presented. The novel idea can have significant contribution in the field of biosensing, although experimental data is still required for the practical discussions of the idea.