Millimeter-wave TX phased array with phase adjusting function between transmitters for hybrid beamforming with interleaved subarrays

We demonstrate a 60-GHz CMOS eight-element TX phased array chip for hybrid beamforming with interleaved subarrays to realize spatial division multiple access. The phased array chip has a function to accurately adjust output phases and amplitudes at each antenna element. Its function has been achieved by finely setting the gate bias voltage of all millimeter-wave circuits using a 64-channel 10-bit digital-to-analog converter and by sensing the output port power and phase difference between ports using a power detector and a phase difference detection mixer. Moreover, the chip has another mixer for phase difference detection between chips. Using this mixer in collaboration with on-chip phase shifters or baseband phase rotators, the beamforming system can achieve phase adjustment between multiple subarray transmitter chips even if the phase difference between these transmitters has changed. We also demonstrate a 16-element two-user hybrid beamforming antenna board. It has achieved a signal-to-interference ratio of over 20 dB around own beam using an interleave subarray configuration.