Multibeam Pillbox Antenna With Low Sidelobe Level and High-Beam Crossover in SIW Technology Using the Split Aperture Decoupling Method

A novel dual-layer multibeam pillbox antenna with a slotted waveguide radiating part in substrate-integrated waveguide (SIW) technology is proposed. In contrast to previous works, the design goal is to have a multibeam antenna with arbitrary low sidelobes and at the same time a high crossing level between adjacent radiated beams. These two constraints cannot be satisfied simultaneously for any passive and lossless multibeam antenna systems with a single radiating aperture due to beam orthogonality. Here, this limitation is overcome using the “split aperture decoupling” method which consists in using two radiating apertures. Each aperture is associated with a pillbox quasi-optical system with several integrated feed horns in its focal plane so as to steer the main beam in the azimuthal plane. The antenna operates at 24.15 GHz and presents very good scanning performance over an angular sector of ±40°, with a good agreement between full-wave simulations and measurements. The crossover level between adjacent beams is about -3 dB with a sidelobe level lower than -24 dB for the central beam and better than -11 dB for the extreme beam positions. The isolation between feed horns in the same pillbox system is better than 20 dB.