Wideband Unidirectional Antenna of Folded Structure in Microwave System for Early Detection of Congestive Heart Failure

A three-dimensional antenna based on a combination of loop and dual monopole structures with parasitic elements is presented. The antenna is specifically designed for a microwave system aimed at the early detection of congestive heart failure. The antenna is first designed as a planar structure and then folded over optimally defined folding lines to properly alter the path and phase of the surface currents for a unidirectional radiation and compact size as needed for the detection system. A prototype antenna of size 0.29λ × 0.08λ × 0.08λ (where, λ is the wavelength of the lowest resonant frequency) is developed to cover the band required in the targeted application. The measured results indicate 53% fractional bandwidth (580 - 1000 MHz), 6-8 dB front to back ratio, and 3-5 dBi gain. The antenna is then used to build a heart failure detection system, which also includes a compact microwave transceiver, a processing and image reconstruction algorithm based on the synthetic aperture focusing technique, and a display unit. The system is used to successfully detect an early case of congestive heart failure in an artificial torso phantom that includes the main torso organs (lungs, heart, ribs, and fat).