A 28 GHz 8-channel Fully Differential Beamforming IC in 65nm CMOS process

This paper proposes a 28 GHz 8-channel fully differential beamforming IC in a commercial 65 nm CMOS technology for 5G beamforming system. The differential 8-channel beamforming IC consists of 6-bit differential phase shifters, 3-bit differential attenuators, differential 2-stage bi-directional amplifiers (BDAs) with variable gain control and differential 2-way power divider. The cross-connected quad switch for the 180° phase bit is implemented with low insertion loss and compact chip size compared with its conventional filter type 180° phase bit. The transmitter mode overall gain and return losses of the differential 8-channel IC are 12.2 dB and > 10 dB at 27.0-29.5 GHz, respectively. The receiver mode overall gain and return losses of the differential 8-channel IC are 12.2 dB and > 10 dB at 27.0-29.5 GHz, respectively. The maximum phase of 354°with 5.6°step and the maximum attenuation of 31 dB with 1 dB step are achieved at 27.0-29.5 GHz. The RMS phase and amplitude errors are <; 3.5°and <; 0.4 dB at 27.0-29.5 GHz, respectively. The output P1dB of > -2.5 dBm and the saturation power (P
_SAT
) of > 1.0 dBm are achieved at 27.0-29.5 GHz. The chip size is 3.0 x 3.5 mm
²
including pads, and the DC current consumption is around 580 mA at 2.5 V supply voltage.