Cross-Configuration Substrate Integrated Waveguide Beamforming Network for 1D and 2D Beam Patterns

This paper presents the simulated and measured results of a dual-layer substrate integrated waveguide (SIW) beamforming network utilizing an 8 × 8 cross-configuration Butler matrix over a frequency range of 28.5 to 31.5 GHz. By arranging the input ports on the bottom SIW layer and employing dual-layer passband filters as a detachment point, the top SIW layer can be interchanged with the purpose of exploring one-dimensional and two-dimensional broadside beam patterns. Although Butler matrices are not typically utilized for beamforming in this configuration, two examples of interchangeable top layer arrays are demonstrated; the first being a 2 × 8 slot antenna array for 1-D scanning, and the second being a 2 × 4 center-slot array for 2-D scanning. Each of the beamforming network's simulated and measured 10 dB bandwidth is demonstrated over a range of 28.5 to 31.5 GHz. Additional design details and dimensions are specified for the aforementioned passband filter transitions, as well as for each of the slot antenna arrays.