Compact 3-D Antenna for Medical Diagnosis of the Human Head

A compact 3-D antenna for microwave medical diagnosis is presented. The antenna is matched with an inhomogeneous human head allowing higher signal penetration so as to obtain more meaningful data reflected from inside the brain. Utilizing a folded inverted F-like structure and a slot-loaded ground plane, the antenna is a compact 0.23 λ×0.23 λ×0.04 λ in size with respect to the lowest operating frequency. The antenna is backed with a rectangular cavity to minimize sidelobe and backlobe radiation. The cavity and folded antenna configuration achieve a highly directional radiation pattern toward the head with a front-to-back ratio of more than 17 dB. A curved inhomogeneous human head phantom is fabricated to validate the antenna performance for medical diagnosis applications. An operational frequency band from 1 to 1.7 GHz is achieved with the antenna attached to the surface of the phantom. Less than 0.0147 W/kg SAR is achieved throughout the operating frequency range, which is lower than the state of the art for comparable antennas. The salient characteristics of the proposed antenna make it a suitable candidate for microwave diagnosis of the human head.