Near-Field Focusing With Bi-Directionally Fed Frequency-Scanned Antennas for Proximity Sensing

The application of one-dimensional bi-directional fed frequency-scanning leaky-wave antennas for proximity sensing is studied in this work. Using the two opposite ports of a microstrip antenna, a nearfield focused radiation pattern which varies with frequency is obtained. This type of frequency-diverse pattern can be used for sensing in the Fresnel region of the antenna. A simple half-width microstrip leaky-wave antenna with 35 cm of length is designed to operate in the 5.5 GHz band. The successful synthesis of nearfield focusing patterns on the proximity of the antenna, and which strongly vary in the frequency range from 5.18 GHz to 5.72 GHz, is theoretically and experimentally demonstrated. Finally, it is illustrated how this type of antenna can be applied to sense in a region of 50 cm x 50 cm surrounding the aperture.