Abstract
In this paper, a miniaturized implantable circularly polarized spiral Planar Inverted-F Antenna (SPIFA) in the UHF (600-800 MHz) band is presented. This antenna is intended for deep implantable devices such as leadless pacemakers and deep brain stimulation (DBS), which facilitates the reception of RF power from an external transmitter. The antenna is electrically small, with a volume of π × 5 mm x 5 mm × 3.2 mm and a diameter of 0.022λ. The performance of the proposed antenna in terms of reflection coefficient, realized gain and axial ratio are assessed when accounting for the effects of operating in different types of human body tissues, different biocompatible materials and different thicknesses and depths of the implanted antenna. Finally, the antenna is prototyped and measured in free space, a phantom model, in a cow's fat and muscle tissues to validate the simulation results, indicating good agreements. A realized gain around -20 dBm is achieved when operating in 50 mm depth in cow's muscle tissue while having electrically very small dimensions compared to implantable antennas reported in the literature.
Highlights
Wireless technologies and communication are nowadays involved in every aspect of human life, and includes areas such as telemedicine and implants [1]
MEASUREMENT OF REFLECTION COEFFICIENT Measurements of reflection coefficient and the resonant frequencies of the encapsulated spiral Planar Inverted-F Antenna (SPIFA) are performed under three scenarios
It is measured inside a phantom model which mimics the electrical properties of muscle tissue at the operating frequency [49], while being connected to a Vector Network Analyzer (VNA) at the other end
Summary
Wireless technologies and communication are nowadays involved in every aspect of human life, and includes areas such as telemedicine and implants [1]. RF links are able to transfer power and high data rate signals [4], [5] Such RF-link approach is already applied in a variety of applications, including blood-glucose monitoring [6], [7], pacemakers [8]–[10], and retinal. The frequency band is selected based on the licensed frequencies (such as MICS and ISM) [13]–[19] This method of selection may not be optimal for the application in question [4], [20]. This is due to their orientation and polarization independence between the transmitter and the receiver [13], [14], [17]–[19], [21], [22]
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