Flat-topped pattern synthesis of optical leaky-wave antennas

Abstract

In this article, a synthesis procedure is proposed to achieve a flat-topped radiation pattern in optical leaky-wave antennas (OLWAs). In the proposed procedure, the antenna is divided into sections, each with an appropriate phase constant, length and leakage constant. By determining a proper value for these parameters, the desired flat-topped pattern is achieved. The phase constant of the sections is obtained such that their beam pointing angle follows an appropriate layout in the region of interest. Further, by introducing the same beamwidth and the same radiation power for the radiating sections, the two latter parameters, i.e., the length and the leakage constant of the sections are determined. The proposed synthesis procedure is applied to a conventional OLWA, i.e., grating waveguide (GWG), to achieve a flat-topped pattern in the angular region of -30°to -11°. Results show that the desired radiation pattern is well synthesized. Finally, the effects of beam spacing and the sections’ beamwidth on the angular rejection slope, symmetry level, -3 dB and -10 dB beamwidth are investigated. The reflection coefficient of the synthesized antenna is also examined, indicating an excellent operation below -38 dB at the entire frequency band. The proposed synthesis procedure can be applied to any type of OLWA, through which a uniform illumination can be achieved in a desired angular region.