A Double-Layer Multibeam Antenna With 45° Linear Polarization Based on Gap Waveguide Technology

In this article, a double-layer 1-D multibeam antenna based on gap waveguide (GWG) technology is proposed. The bottom layer is the beamforming network (BFN), which is composed of four cruciform couplers and two −45° phase shifters realized by groove GWGs. Four output ports of the BFN are connected to the slot arrays on the top layer through 180° E-plane bends. The output amplitudes of the BFN are −6.3 ± 0.5 dB and the phase errors are within ±14° from 26 to 32 GHz with a bandwidth of 20%. To relieve the grating lobe problem, groove GWGs are transited to ridge GWGs on the top layer and the slot array is fed from ridge GWGs. Due to the topology of the BFN, the slot array is oriented along the diagonal plane and as a result, the multibeam antenna is 45° linearly polarized. To handle the dip emerging in the side beam caused by the finite ground of the BFN, several metal fences working as a soft surface are applied to suppress the edge diffractions. Besides, the gain is increased by 0.78 dB compared to the case without metal fences at 29 GHz. Thanks to the low-loss property of GWG technology, high gain, and high radiation efficiency are obtained. The maximum gain is 17.46 dBi with the beam direction at −11° for Port 1 and 16.51 dBi with the beam direction at 37° for Port 2. The simulated radiation efficiency is above 97% for both Port 1 and Port 2.