A 28 GHz fully differential eight-channel beamforming IC (BFIC) with multimode operations is implemented in 65 nm CMOS technology for use in phased array transceivers. The BFIC has an adjustable gain and phase control on each channel to achieve fine beam steering and beam pattern. The BFIC has eight differential beamforming channels each consisting of the two-stage bi-directional amplifier with a precise gain control circuit, a six-bit phase shifter, a three-bit digital step attenuator, and a tuning bit for amplitude and phase variation compensation. The Tx and Rx mode overall gains of the differential eight-channel BFIC are around 11 dB and 9 dB, respectively, at 27.0-29.5 GHz. The return losses of the Tx mode and Rx mode are >10 dB at 27.0-29.5 GHz. The maximum phase of 354° with a phase resolution of 5.6° and the maximum attenuation of 31 dB, including the gain control bits with an attenuation resolution of 1 dB, is achieved at 27.0-29.5 GHz. The root mean square (RMS) phase and amplitude errors are <3.2° and <0.6 dB at 27.0-29.5 GHz, respectively. The chip size is 3.0 × 3.5 mm2, including pads, and Tx mode current consumption is 580 mA at 2.5 V supply voltage.
Keywords: 28 GHz; CMOS; beamforming; fifth generation (5G); mm wave; multi-channel; multimode; phase and gain control; phased array antenna; transceiver.