A mm-Wave MIMO Transmitter with a Digital Beam Steering Capability Using CMOS All-Digital Phase-Locked Loop Chips

In this paper, we propose a mm-wave transmitter architecture intended for radar and 5G MIMO applications with beam steering over 57–63 GHz frequency band. Each transmitter chain comprises an all-digital phase-locked loop (ADPLL) CMOS IC chip intended to be dictated to a single antenna unit within an array. For demonstration purposes, each IC is embedded on a printed circuit board (PCB) to provide beam steering using highly accurate digital approach. The overall transmitter is connected to an antenna array with half wavelength spaced elements to maximize the beam scanning coverage. The ADPLL boards are fabricated and a calibration technique is carried out to align amplitude-phase of all transmitter channels at the input of the antenna array for beamforming goal. It is demonstrated that phase noise performance of the ADPLLs has considerable impact on the phase-alignment accuracy.