Wideband and Unidirectional Folded Antenna for Heart Failure Detection System

A wideband folded antenna, which is specifically designed for an early heart failure detection system operating at the ultra-high frequency (UHF) band, is presented. The design procedure starts with a planar structure that includes a loop antenna, a dual monopole, and a loaded parasitic patch. To significantly reduce the size of the antenna and achieve directional radiation as needed for the intended application, the planar structure is folded to form a three-dimensional antenna with the dimensions 0.1λ×0.29λ×0.09λ, where λ is the wavelength at the lowest operating frequency. The final tested antenna achieves a peak gain of 4.2 dBi, front-to-back ratio of 7-13 dB and efficiency of more than 87% over 62% fractional bandwidth (560-1060 MHz) at 10-dB return-loss reference. The antenna in addition to a compact microwave transceiver and an adjustable platform are then used to build a monostatic-radar-based heart failure detection system. The system is tested on an artificial torso phantom to verify the potential of such a system in the early detection of heart failure. The used imaging algorithm and obtained promising results are reported in the letter.