A four channel phased array transmitter using an active RF phase shifter for 5G wireless systems
This paper presents a four channel phased array transmitter at 15 GHz aimed for the upcoming 5G wireless systems. The circuit is designed and fabricated using 45 nm CMOS silicon on insulator technology. The design is programmable with exhaustive digital controls available for parameters such as bias voltage, resonance frequency, and gain. The phase shift required for the phased array is provided at RF using an IQ vector modulator (IQVM) topology, which provides both amplitude and phase control. Based on the measurement results, the IQVM provides 360° of phase shift and 15 dB of gain variation. Both phase and amplitude information are encoded in a 10 bit control word. The mean angular separation provided by the IQVM is 3° at optimum amplitude levels. Active area occupied is 2.88 square millimeter. Total DC power consumed by one transmit channel from 1 and 2.6 V supply is 268 mW. The maximum RF output power from one transmit channel is 1dBm. Measured EVM for a 256 QAM modulated signal is as low as 2.0%. All results include the impact of printed circuit board traces and pad parasitics. Based on the achieved results, the proposed architecture is well suited for the next generation of the wireless systems.