A Planar, Broadband, Metamaterial-Based, Transmission-Line Beamformer

A broadband, seven-port beamformer is designed and fabricated using printed-circuit, tensor transmission-line metamaterials. The beamformer is first modeled as a 2-D medium with an unknown inhomogeneous, anisotropic material distribution: scalar permittivity ∈z(x, y) and tensor permeability μ̅(x, y)Then, a recently developed optimization procedure is employed to determine ∈z(x, y) and μ̅(x, y) and subsequently realized using tensor transmission-line metamaterials. The beamformer is designed to switch beams in 10° increments from -30° to 30° in azimuth, over a broad range of frequencies. Measurement results exhibit good agreement with the prescribed design goals. The reported beamformer offers several advantages compared with traditional beamformers, including the stipulation of arbitrary output fields, flat input/output interfaces, and a broad bandwidth performance.