Fast Butler Matrix Evaluation for a Phased Antenna Array
(Room Exhibit Hall A)
18 Oct 18
3:00 PM
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3:30 PM
The Butler matrix is a cost-effective passive beamforming feed network for phased array antenna applications without requiring active devices such as mixers, switches, phase shifters, and transceivers. However, the typical Butler matrix designs need to deploy many air-bridges, vias, and bent cables that result in a complicated prototyping process. It would also be cumbersome to connect the output ports of the beamforming network to an N×1 antenna array where each element is evenly, so extra cables might have to be added, stretched, and bent. In this session, the frequency-domain transmission line equation in the COMSOL Multiphysics® software is used to model an 8×8, and 16×16 Butler quickly. The 8×8 Butler matrix is extended to build a 64×64 input and output channel feed network system. The proposed Butler matrix circuit design accounts for a single layer fabrication without using any air-bridges or metalized vias by utilizing multiple ladder-shaped crossover structures which can be turned into easy-to-fabricate planar microstrip lines and are ready to be connected to an antenna array. The simulation computes the arithmetic phase progression at each output port of the beamforming network and couples the Butler matrix to a full-wave FEM simulation of a patch antenna array on a single-layer substrate. The results show the steerable far-field radiation pattern generated by 8×1, 16×1, and 8×8 patch antenna arrays.