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.