A 60-GHz CMOS 16-beam beamformer for two-dimensional array antennas

A 60-GHz CMOS beamformer for sixteen conical-beam generation in both azimuth and elevation dimensions from planar array antennas is presented. The conventional 4-way Butler matrix allows four beams generated only in one dimension. For two-dimensional generation, two stacks of 4-way Butler matrix are composed to generate 16 beams in azimuth and elevation dimensions. The 16-beam beamformer was implemented in 0.18-μm CMOS technology, where the chip size is 2×2 mm². The progressive phase error between adjacent output ports is 17.6° at 60 GHz, which will result in 3° main-beam direction error. The insertion loss of one path is 4.7 dB. The overall array gain is 6.5 to 8.4dB.