A 28 GHz CMOS Butler matrix for 5G mm-wave beamforming systems

This paper presents 28 GHz CMOS 8x8 Butler matrix which can improve the beamforming capability in 5G mm-wave communication systems. The proposed 28 GHz NxN Butler matrix can increase the number of the antenna beam pattern from N to 2N - 1 beams with DP8T switch network including a lumped 180 degrees coupler, 22.5 degrees phase shifter, and switches. The beamformer is fabricated using 65 nm CMOS process and the size is 1.8 x 2.5 mm(2). The DC current consumption is 145 mA (Rx) and 180 mA (Tx) at 2.5 V supply voltage. The proposed 28 GHz CMOS 8x8 Butler Matrix is able to make 15 beam patterns with +/- 63 degrees beam scan and low sidelobe level, which is suitable in low cost 5G mm-wave beamforming system.