Holographic Surface Leaky-Wave Lenses With Circularly-Polarized Focused Near-Fields—Part II: Experiments and Description of Frequency Steering of Focal Length

This paper reports experimental results which demonstrate the possibility to synthesize focused near-fields from a planar printed circuit which is fed with a simple coaxial probe. A prototype operating at 10 GHz has been manufactured and tested. As predicted by the theory described in the first part of this paper, high 75% focusing efficiency of circularly polarized fields is obtained as a result of the proper modulation of the dimensions of the Archimedean-shaped printed slot. The designed coaxial feeding provides good matching (below
$-10~{\rm dB}$
) in the entire frequency band. Finally, the scanning of the focal length as a function of the frequency is described in this paper, showing measured results and accurate theoretical explanation based on the frequency dispersion of the tapered leaky mode. This phenomenon is general for this type of two dimensional leaky-wave lenses, and might find many applications in imaging, sensing and heating.