Design of UWB antennas to monitor cardiac activity

This paper presents two novel ultra wideband (UWB) printed antennas designed to be part of a UWB radar system for cardiac activity monitoring. The two antennas have the same shape but differ in terms of dielectric substrate and dimensions and are designed to be used one in a wearable and the other in non-wearable (fixed) radar. With regard to the fixed antenna, numerical results show an optimum fidelity factor and an almost constant group delay in the 3.1 - 10.6 GHz frequency band. As concerns the wearable antenna, numerical results obtained considering the antenna placed in the vicinity of a box model of the thorax, containing a spherical model of the heart, show that small heart movements can be detected. Eventually, the two antennas have been realized and measured by means of a vector network analyzer finding a return loss lower than -10 dB in the 3.1 - 10.6 GHz frequency band with a good agreement between simulations and measurements. Also, measurements of the fixed antenna gain and radiation pattern, performed in an anechoic chamber, show a good agreement with simulations.