Human tissue type and volume effect on the on-body UWB antenna matchings

摘要

This article examines the effect of divergent human tissue types and volumes on the matchings of ultra-wideband (UWB) antennas. The work is based on measurements in an anechoic chamber with a vector network analyzer by sweeping a frequency range of 2¿¿¿8 GHz. Two planar prototype UWB antenna types were applied: the dipole and the double loop antenna. The antennas were attached at a 20 mm distance from the body at fourteen spots. The locations under the antennas represent various human tissues under the skin with varying compositions of fat, muscle and bone and different volumes of the tissues. They are selected based on the existing or easily assumed spots for various on-body sensors. The matchings are defined by observing the scattering parameter S11 corresponding to the voltage reflection coefficient of an antenna. A matching is considered good if the S11 value is smaller than ¿¿¿10 dB. The tissues change the matchings by decreasing the lower frequency limit by up to 100 MHz, depending on the tissue type, volume or the antenna type, compared to the free space result. The differences between tissue types or tissue volumes are minor, no notable effects on the antenna matchings can be observed. The tissues have a stronger influence on the double loop antenna matchings compared to the free space than on the dipole antenna.