Millimeter-Wave Dual Left/Right-Hand Circularly Polarized Beamforming Network

A novel high-efficiency eight-beams dual-polarized array antenna using an 8 × 8 beamforming network is studied and developed at 60 GHz. Two 4×4 Butler matrices are employed as base beamformers, and two 4×8 pattern control networks are utilized for increasing the number of radiating elements and suppressing sidelobes in the proposed dual left/right-hand circularly polarized (LH/RH CP) beamforming network. This beamforming network is implemented in hedgehog and hollow waveguide technologies using the diffusion bonding technique. Diffusion bonding, also known as diffusion welding, is a solid-state joining process that is based on the atomic diffusion of elements at the joining interface. The progressive slot technique is used as a traveling-wave antenna for generating a wideband axial ratio at 60 GHz band from 57 to 64 GHz. The sidelobes are suppressed to lower than -19 dB across the visible scanning range. The operating bandwidth of the system is 10.75% at 60 GHz, and the radiating efficiency of the system is above 90% for each port. The beamforming network is fabricated and measured. The simulated and measured results show a good agreement.