A novel compact UHF wideband antenna for near field electrical characterization of Steel Fiber Reinforced Concrete

A novel, electrically small, UHF (350 MHz-750 MHz) microstrip slot antenna is presented. The antenna is designed for the characterization of steel fiber reinforced concrete (SFRC) segments. The antenna consists on a three layer structure headed by the slot ground plane, followed by the feeding microstrip in the central layer with some resistive loading for bandwidth enhancement purposes; finally on the bottom layer a strip line reflector is positioned to provide a unidirectional radiation pattern, required for harsh environments. The whole design has been optimized in front of SFRC for maximum impedance bandwidth. Input impedance and radiation pattern are studied both theoretically and experimentally, and some laboratory measurements have been done on real SFRC specimens. Satisfactory results for the fiber density of SFRC are presented.