Experimental Validation of Bessel Beam Generation Using an Inward Hankel Aperture Distribution

In this paper, we prove experimentally that nondiffractive Bessel beams can be generated by using inward cylindrical traveling wave aperture distributions. An azimuthally invariant inward traveling wave distribution is defined over the aperture of a radial line slot array (RLSA) to launch a Bessel beam whose normal electric-field component assumes a truncated, zeroth-order Bessel function. An optimization procedure based on a holographic approach is used for tuning the position and size of the slots of the RLSA. The antenna is centrally fed by a coaxial probe transition. The final structure operates at 12.5 GHz. Full-wave simulations and measurements of the vertical component of the electric field show that a non-diffractive radiation is obtained within a range larger than 12 wavelengths in front of the antenna. The generated Bessel beam presents a stable half-power beamwidth of about 20 mm within this range. The proposed system may open new opportunities for planar, low-profile Bessel beam generators at millimeter waves, Terahertz, and optics.