Experimental Characterization of UWB Antennas for On-Body Communications

In this paper, the radiation of three types of ultrawideband (UWB) antennas is experimentally characterized for near/on human body scenarios. The transmission performance for vertical and horizontal polarizations is measured at different body orientations. The received pulses are analyzed in the time domain by selecting Dirac impulse and sine-modulated Gaussian monocycle as source pulses. The peak-to-peak amplitudes, fidelity, and stretch ratio of the waveforms of the received pulses are computed based on the measured results. In measurements, three types of UWB antennas are studied, namely an omnidirectional monopole antenna, directional suspended plate antenna, and printed diversity antenna. From the study, it is found that the omnidirectional antenna experiences an increase in the transmission due to the reflections from the body but suffers from narrower horizontal coverage due to a higher attenuation as the body turns away from the transmit antenna compared to the directional antenna. However, the directional antenna is less sensitive to the distance of the antenna away from the body in vertical and horizontal polarizations. The diversity antenna is able to maintain high peak-to-peak amplitudes in the waveforms of received pulses for both polarizations and the high fidelity when it is placed near the body. Therefore, the printed diversity antenna is suitable for on-body-centric communications with improved quality of the overall radio-frequency link.