Compact 2-D Beam-Scanning Multibeam Antenna Based on Modified Partial Maxwell Fish-Eye

A compact 2-D beam-scanning multibeam antenna based on a modified partial Maxwell fish-eye (PMFE) is proposed in this letter. The antenna comprises a modified PMFE beamforming network and leaky-wave antennas array. The conventional half Maxwell fish-eye is redesigned using ray-tracing method by increasing the refractive index at the lens rim to values greater than one, which facilitates simple fabrication with printed circuit board technology. The PMFE is discretized into a series of concentric rings: inner rings are filled with air-hole unit cells, while outer rings consist of split-ring resonator unit cells. This design not only maintains a wide bandwidth but also achieves a refractive index as low as possible. To enhance the scanning rate, a substrate integrated waveguide-based spoof surface plasmon polaritons transmission line is used to excite two longitudinally identical slots. A prototype is fabricated and measured. The results show that the proposed antenna achieves a frequency-controlled beam scanning range from -56° to 58° with a scanning rate of 5.8, and a multibeam scanning range from -39° to 37°.