Tissue-implanted ultra-high frequency (UHF) radio devices are being employed in both humans and animals for telemetry and telecommand applications. This paper describes the experimental measurement and electromagnetic modeling of propagation from 418-MHz and 916.5-MHz sources placed in the human vagina. Whole-body homogeneous and semi-segmented software models were constructed using data from the Visible Human Project. Bodyworn radiation efficiencies for a vaginally placed 418-MHz source were calculated using finite-difference time-domain and ranged between 1.6% and 3.4% (corresponding to net body losses of between 14.7 and 18.0 dB). Greater losses were encountered at 916.5 MHz, with efficiencies between 0.36% and 0.46% (net body loss ranging between 23.4 and 24.4 dB). Practical measurements were in good agreement with simulations, to within 2 dB at 418 MHz and 3 dB at 916.5 MHz. The degree of tissue-segmentation for whole-body models was found to have a minimal effect on calculated azimuthal radiation patterns and bodyworn radiation efficiency, provided the region surrounding the implanted source was sufficiently detailed.

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Current and emerging indoor radio communications systems are designed to operate at microwave fiequencies and above. As fiequency is increased, fading effects caused by the movement of personnel become more significant over short-range channels. This paper examines pedestrian-induced fading characteristics at key ISM fiequencies within the microwave band. Consideration is given to the effects of wave obstruction by the human body -reflection, difiaction and transmission. Fading profiles are reported for a point-topoint link in a 150-m' open-plan environment with moderate pedestrian trafic conditions. Irrespective of simulation frequency, the calculated fading projiles were loosely correlated and fading depths ranged between 31-dB and 36-dB. The results were Rayleigh distributed despite the presence of a direct-ray for the majority of the simulated period.

The electrical and communication performance of a 0.8-microW UHF temperature telemeter designed for human vaginal placement is discussed; a solenoidal loop antenna was used, occupying a volume of 0.1 cm3. In situ, measured power absorption was between 19-25 dB, resulting in an effective operating range of 10 m. Capacitive loading lowered the antenna's resonant frequency by 1.4% and there was a significant polarization change in the radiated output.