This paper describes the finite-difference time-domain (FDTD) analysis of a
ntenna-body interaction effects occurring when chest-mounted 418 MHz radio
transmitters are used for medical telemetry applications. Whole-body softwa
re models (homogeneous, layered and tissue-segmented) were developed for an
adult male subject. Using an electrically small (300 mm(2)) planar loop an
tenna, calculated radiation efficiencies ranged between 33.5% and 39.2% for
a whole-body model, and between 60.7% and 66.1% for a torso; radiation pat
terns were found to be largely independent of model composition. The comput
ed radiation efficiency for a 21.5 kg phantom representing a six-year-old f
emale was within 1.1 dB of measured results (actual body mass 28 kg) and we
ll-correlated azimuthal radiation patterns were noted.