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Abstract-In implanted biomedical devices, due to the presence of surrounding dissipative biological tissue, the antenna suffers poor impedance matching. This causes degradation in the performance of a wideband or ultra-wideband (UWB) implanted device. Moreover, the electrical properties of tissue change from organ to organ, and possibly from time to time. In this paper, it is shown that loading of antennas with suitable insulators can deliver broadband matching across a range of dissipative medium properties. An impedance-matched UWB antenna designed to operate inside a lossy medium, which has varying electromagnetic properties within the range expected in biological tissues, is presented. The operating bandwidth of the proposed design is 3.5-4.5 GHz, which is an interference-free subset of the unlicensed UWB band in the US. It is demonstrated that once the dielectric loading is applied, the conventional procedure for antenna design in free space can be followed. The proposed implantable small capsule-shaped slot antenna has been characterized using numerical simulations. Details of a proof-of-concept experiment are presented.Index Terms-Biomedical electronic, biomedical engineering, implanted device, ultra-wideband (UWB) antenna.

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Abstract-A compact, printed, capsule-shaped ultrawideband (UWB) antenna for biomedical implants is presented. The 10-dB return loss bandwidth of the proposed antenna is 3.5-4.5 GHz, which covers the recently proposed UWB for biomedical applications. The antenna matching has been optimized using CST Microwave Studio and verified by measurements. An optimized feed mechanism to reduce guided wavelength, as well as integration with other electronics, has been considered in the antenna design. Radiation performance has been evaluated on an impulse-based UWB transmitter/receiver testbed to show that the antenna is usable in biomedical applications, such as capsule endoscopes. The antenna has been tested both in free space and with tissue loading.

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