A compact dual-polarized triple-band antenna for implantable Biotelemetry applications

In this paper, a dual-polarized triple-band antenna for implantable biotelemetry application is presented. The antenna exhibits linear polarization (LP) characteristics at 404 MHz and 916 MHz while circular polarization (CP) characteristics at the 2.43 GHz band with a footprint of 0.0473 $ \lambda _{g} \times $ lambda gx 0.0387 $ \lambda _{g} \times $ lambda gx 0.0022 $ \lambda _{g} $ lambda g where $ \lambda _{g} $ lambda g is the effective wavelength. The proposed antenna exhibits an overall dimension of 11 mm x 9 mm x 0.5 mm (volume of 49.5 mm3). The dual polarization feature of the proposed antenna can specifically address the diverse polarization requirements of specific applications. A conceptual equivalent circuit model of the proposed antenna has also been developed to understand the effect of human tissue loading on the antenna characteristics. Moreover, characteristic mode analysis (CMA) has been employed to understand the intrinsic radiation feature and polarization phenomenon of the proposed antenna structure. The measured response shows a -10 dB impedance bandwidth of 56 MHz covering the MICS band, and 122 MHz and 220 MHz covering the lower and upper ISM band with a maximum gain of -26.4 dB, -24.4 dB, and -22.6 dB respectively. The proposed antenna's specific absorption rate has been evaluated, which complies with the safety regulation for implantable scenarios. The link margin also assesses the communicable range of the proposed antenna for biotelemetry. The proposed antenna is capable of transmitting data at 7 kb/s and 100 kb/s up to a distance of 13 m and 3.5 m, respectively. In vitro measurement has been performed to validate the proposed antenna performance, and the measured result agrees well with the simulated one.