Directive 2-D Beam Steering by Means of a Multiport Radially Periodic Leaky-Wave Antenna

A multifed radially periodic two-dimensional leaky-wave antenna is proposed for the generation of a directional beam continuously scanning in elevation by changing the frequency, and over a discrete number of directions in azimuth when activating different elements of the feeding system. The structure is planar and constituted by a circular grounded dielectric slab loaded with microstrip rings, properly positioned around the sources to support the propagation of an angularly directional surface wave over a sector determined by the corresponding activated feeder. This produces a perturbation of the surface wave, resulting in the generation of a directional leaky wave over the aperture, whose complex propagation constant is described by a single fast backward spatial harmonic. The antenna radiation features are numerically investigated in conjunction with the dispersion analysis of the structure, validated through a conventional generalized-pencil-of-function approach. Full-wave simulations have been developed to design a practical feeder, which is constituted by a circular arrangement of commercial coaxial connectors. The proposed multiport antenna is validated by means of measurements performed on a microwave manufactured prototype. The design represents an attractive simple and cost-effective solution to achieve a high-gain beam scanning over the three-dimensional space, alternative to more conventional phased-array design based on cumbersome and lossy feeding networks.