A 28-GHz CMOS Phased-Array Beamformer Utilizing Neutralized Bi-Directional Technique Supporting Dual-Polarized MIMO for 5G NR

This article presents a low-cost and area-efficient 28-GHz CMOS phased-array beamformer chip for 5G millimeter-wave dual-polarized multiple-in-multiple-out (MIMO) (DP-MIMO) systems. A neutralized bi-directional technique is introduced in this work to reduce the chip area significantly. With the proposed technique, completely the same circuit chain is shared between the transmitter and receiver. To further minimize the area, an active bi-directional vector-summing phase shifter is also introduced. Area-efficient and high-resolution active phase shifting could be realized in both TX and RX modes. In measurement, the achieved saturated output power for the TX-mode beamformer is 15.1 dBm. The RX-mode noise figure is 4.2 dB at 28 GHz. To evaluate the over-the-air performance, 16 H+16 V sub-array modules are implemented in this work. Each of the sub-array modules consists of four 4 H+4 V chips. Two sub-array modules in this work are capable of scanning the beam from -50° to +50°. A saturated EIRP of 45.6 dBm is realized by 32 TX-mode beamformers. Within 1-m distance, a maximum SC-mode data rate of 15 Gb/s and the 5G new radio downlink packets transmission in 256-QAM could be supported by the module. A 2 × 2 DP-MIMO communication is also demonstrated with two 5G new radio 64-QAM uplink streams. Thanks to the proposed area-efficient bi-directional technique, the required core area for a single element-beamformer is only 0.58 mm
²
. Compact and low-cost 5G millimeter-wave MIMO systems could be realized.