Compact Leaky Wave Fed Frequency-Scanning Gradient Index Lens Antenna for Near-Field-Focusing Applications

In this article, a compact antenna structure capable of focusing in the near-field and composed of a gradient index (GRIN) lens and a frequency-scanning, longitudinally slitted waveguide feed is proposed. The slitted waveguide can support traveling waves propagating with both a positive and negative phase constant (
$\beta $
), thereby allowing scanning between the backward and forward quadrants. The scanning is realized by varying the frequency from 26 to 35 GHz achieving a total displacement of the focusing spot of about 125 mm along the
$ {z}$
-direction in the H-plane.