Abstract
We derived a closed-form expression of the maximum power transfer efficiency (MPTE) between a transmitting antenna inside the brain and a receiving antenna outside the head using spherical wave expansion. The derived expression was validated using a FEKO simulation. The properties of the insulator and radiation mode were analyzed in each available medical implant communications service (MICS) and industrial, scientific and medical (ISM) band as a means of increasing the reliability of wireless biotelemetry implementation. Some interesting preceding results in the literature were revisited with the figure-of-merit MPTE. It was also newly found that the effect on MPTE by the physical size and material properties of the insulator in both transverse magnetic (TM) and transverse electric (TE) mode decreases for 2.4 GHz and 5.8 GHz and the loss of the insulator does not have a severe impact on MPTE once the dielectric constant is greater than a certain value. This work can be used as an implanted-antenna design guide for building reliable biotelemetry communication.
Highlights
Treatment of brain diseases through the analysis of electrical signals from the brain is an interesting research topic
A number of implanted antennas for biotelemetry systems are currently being studied [4,5,6,7]. They are a multi-layered spiral antenna operating in the MedRadio band (401–406 MHz), an industrial, scientific and medical (ISM) band at 2.4 GHz [4], a planar-inverted F antenna operating in the medical implant communications service (MICS: 402–405 MHz) band, an ISM band at 900 MHz [5], a circular polarized patch antenna operating in the 2.4 GHz ISM band [6] and a microstrip patch antenna operating in the ultra-wideband (UWB: 3.1–10.6 GHz) [7]
We study the properties of the insulating layer of the implanted antenna as a means of minimizing path loss to the external antenna of the monitoring system in the MICS and relevant ISM
Summary
Treatment of brain diseases through the analysis of electrical signals from the brain is an interesting research topic. Due to its small size, the implanted antenna generally radiates the lowest mode only and its radiation characteristic in the presence of a lossy medium, such as one of the human tissues, can be analyzed using spherical wave expansion This spherical wave analysis can be used when the transmitting antenna is located inside the human tissue [8,9,10,11], but when it is located outside as well [12,13]. We study the properties of the insulating layer of the implanted antenna as a means of minimizing path loss to the external antenna of the monitoring system in the MICS and relevant ISM bands To this end, we derive a closed-form expression of maximum transfer power efficiency (MPTE). Some preliminary results have been briefly discussed in [16]
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