A low-profile SIW multi-beam antenna array fed by a compact two-layer 6 x 6 BFN

This paper presents a low-profile six-beam antenna implemented by a compact two-layer 6 x 6 beamforming network (BFN) and a 6 x 2 slot antenna in substrate integrated waveguide (SIW) technology. The main components of the proposed 6 x 6 BFN are 3 x 3 multi-aperture couplers, interlayer hybrid couplers, and several phase shifters which are embedded on two microwave substrates. The proposed antenna has been designed, simulated, and fabricated for the frequency range of 28-32 GHz. The size of this antenna is 82 x 31.8 x 0.787 mm3, which can be a suitable choice for 5G applications due to its compact dimensions compared to similar works. Prototype testing shows that the proposed structure presents a stable beamforming performance both in simulation and measurement with good agreement. The antenna generates six radiation beams in directions +/- 9 degrees, +/- 30 degrees, and +/- 54 degrees with good return losses and isolations.