3-18 GHz compact planar antenna for short-range radar imaging

An ultra-compact planar antenna aiming to be part of an imaging antenna array operating in the broad 3-18 GHz frequency range is presented. The antenna is made of two closely packed wide-band monopoles for simultaneous transmission and reception functionalities. A high isolation (>20 dB) between the two patches is achieved through the insertion of a structured ground plane (decoupling structure). A prototype was fabricated on a Roger R4003c laminate measuring 58 × 33 mm² and used in inverse synthetic array radar configuration for detecting a steel object with sub-centimetre spatial resolution.