A 4 × 4 5–6-GHz Analog Beamforming Wi-Fi Transceiver Front End for Fiber to the Room in 55-nm CMOS

This article presents a $4\times 4~5$ –6-GHz CMOS Wi-Fi transceiver (TRX) front end for fiber-to-the-room (FTTR) applications with analog beamforming (BF), which can significantly alleviate indoor signal interference by enabling directional radiation and fine gain control. In addition, due to the higher gain of directional antenna arrays, the effective isotropic radiated power (EIRP) of the beamforming fiber to the room (BF-FTTR) is better than that of the omnidirectional radiation architecture realizing superior linearity at lower power consumption, relaxing the dependence on digital predistortion (DPD). Furthermore, a matching network merged transmitting/receiving (T/R) switch is described, and an analog linearization technique is proposed for the variable-gain amplifier (VGA) and power amplifier (PA) to suppress the transmitter (TX) nonlinear distortion. In each TRX element, the phase and gain controls are realized by a 4-bit passive phase shifter (PS) and a 5-bit passive attenuator (ATT), respectively. Fabricated in a 55-nm CMOS process, the measured saturated output power and the output power 1-dB compression point of the TX are better than 21.8 and 19 dBm at 5.2 GHz, respectively. The error-vector-magnitude (EVM) floor of the TX at the 5-dBm output power with MCS11 signals is −45 dB, and the EVM floor of the receiver (RX) at −25-dBm input power is −48.8 dB. The maximum EIRP of the TX is 27 dBm, with the EVM below −35 dB. The noise figure (NF) of the RX is 4.3 dB.