Compact UHF wide slot antenna for microwave stethoscope designed for heart failure detection

A wide-slot antenna to be used in a compact microwave stethoscope for heart failure detection system is presented. The proposed antenna is based on the conventional slot antenna. However, changing the slot´s shape and modifying the surface current path and consequently changing the electric field distribution inside the slot, provides the antenna with a broadband operation and a compact structure. To accomplish the unidirectional radiation pattern necessary for the heart failure detection system, a series of copper posts connected at certain positions to the reflector is employed to both suppress the back radiation and keep the antenna´s profile low. The proposed antenna has a wide operating bandwidth of 16 % (822-966 MHz), maximum gain of 3.1 dBi and efficiency of over 90 %. The overall size of the antenna is 0.27 λ × 0.19 λ × 0.05 λ, where λ is the wavelength at the first resonance of the antenna.