Out-of-Plane Fed Elliptical Slot Array for Microwave Imaging

In this communication, a new approach for feeding a PIN diode-loaded resonant elliptical slot used in microwave imaging arrays for nondestructive testing applications is considered. The proposed feed is based on coupling the transmitted and received signals into the slot using an out-of-plane (perpendicular) microstrip line. An imaging array prototype with this slot, a 90 °-bent microstrip-line feed and a coplanar waveguide (CPW) to microstrip line transition was designed and experimentally validated. The design readily accommodates placement of the switching and PIN diode biasing networks on the feeding plane using CPWs, enabling one-sided imaging measurements. The relevant design steps and imaging results obtained with this prototype, in mono-static and bi-static modes, are presented.