A Compact Multichannel Implantable Antenna for High-Speed Telemetry

In this article, a compact two-port dual band multiple-input–multiple-output (MIMO) antenna system is presented with a very small physical size of $5.7\times 5.7\times 0.13$ mm³. The electrical volume of the proposed antenna is found to be $0.0000038\lambda _{g}^{3}$ . The proposed antenna system resonates at 915 and 1610 MHz, with 10-dB absolute bandwidths of 157 and 217 MHz, respectively. The MIMO system consists of two side by side spiral and meandered antenna elements. Edge to edge distance between both radiators is 0.4 mm, which accumulates to $\approx 0.0012$ and $0.00215\lambda $ at guided wavelengths of 915 and 1610 MHz, respectively. The isolation level is better than 34.2 and 27.5 dB for both resonating bands, respectively. The effectiveness of the MIMO system is demonstrated through an analysis of the specific absorption rate (SAR), link budget, and MIMO channel parameters. Channel parameters were calculated and validated in $2\times 2$ MIMO configuration, achieving a channel capacity of 8.45 bps/Hz at a signal-to-noise ratio (SNR) of 20 dB. A prototype was fabricated and tested using saline solution to verify the simulation results. The findings suggest that the proposed MIMO system can find its applications in implantable capsule endoscopy and other biotelemetry applications where high speed is desirable. To the authors’ knowledge, this is the most compact dual-band implantable antenna designed so far.