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Evaluation of a new radio frequency identification tag for subdermal implantation Azad, Farhan

Abstract

This research was aimed at examining the readiness of a prototype implantable tag of dimensions 39 mm x 24 mm x 4.1 mm designed to operate at 915 MHz for monitoring the movement of young sea lions and seals. Several issues had to be resolved, and they include developing and testing a suitable communication protocol between the base station and tag, and way of providing power to the tag. Engineering issues related to longevity of the implantable tag, and power radiated by the loop antenna of the implantable tag in its alumina enclosure, under skin and under the fat underlying the skin, also, had to be addressed. Finally issues related to how data from the tag could be best recorded at haul outs and rookeries were examined. A working prototype of an implantable tag was obtained by reducing the height of the loop antenna by 2 mm and changing the capacitor values in the matching network to 0.2 pF. Field tests using a base station that accepted signal strengths up to -60 dBm indicated that the tag’s range was a maximum of 500 m when it was operated out of a body at a data rate of 1 kbps and the height of the base station antenna was more than 5 m. When the prototype was implanted within its alumina housing under the skin of cavernous tissue, the range of the device fell to an acceptable 180 m. A lifetime model indicated that the longevity of the tag would meet the three year target if it were to be operated using a data rate of 1 kbps, transmission interval of 15 min, packet size of 104 bits and battery capacity of 72 mAh. The lifetime model was verified at the same temperature as a sea lion. A link budget model was developed for the prototype tag, and was used to estimate the performance of the implantable in the sea lion’s environment.

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Attribution-NonCommercial-NoDerivatives 4.0 International

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