Characterization of an Intra-Body Wireless Link in the UHF Band

Recent advancement in ultra-low-power electronics and radio communications has significantly contributed to the development of miniaturized biomedical sensors capable of capturing and transmitting wirelessly physiological data. The characterization of signal and power transmission inside the human body is of great importance. This paper investigates the case of an intra-body wireless communication in the UHF frequency band. An implanted antenna (bent dipole) is designed to operate efficiently in a biological tissue model. Predictions of the performances obtained by 3D electromagnetic simulations are compared to measurements in a realistic environment (pork meat in a box of 18 x 10 x 7 cm(3)). The antennas show return loss matching of -12 dB at 1.2 GHz, in the presence of the meat. Then a characterization of the transmission link between two antennas is performed both numerically and experimentally at 1.2 GHz. At this frequency, the measured vertical bar S-21 vertical bar(2) is around -35 dB at 6 cm, and -40 dB at 8 cm. The simulation of the vertical bar S-21 vertical bar(2) highlights the impact of the conductivity of the tissues, driving to values of -25 to -55 dB at 6 cm, and -30 to -65 dB at 8 cm. The characterization of the pork meat conductivity is evaluated experimentally around 2 S/m. During the process of characterization, this value may be over-estimated due to the pressure applied on the sample. The simulations results are compared with measurements results, and also with retro-simulations results. The latter are considered as a worst case due to the losses implied by the over-estimated conductivity value.

Automated summary

This paper investigates the case of an intra-body wireless communication in the UHF frequency band. It designs an implanted antenna that operates efficiently in a biological tissue model and compares the predictions obtained by 3D electromagnetic simulations to measurements in a realistic environment. The results show that the antennas have a return loss matching of -12 dB at 1.2 GHz, and the conductivity of pork meat is evaluated to be around 2 S/m.