A Time-Modulated Concurrent Steerable Multibeam MIMO Receiver Array With Spectral-Spatial Mapping Using One Beamformer and Single-Wire Interface

This work proposes a wideband 26–33 GHz multiple-input- multiple-output (MIMO) receiver (RX) array that leverages time-modulation operation to achieve concurrent steerable multibeam MIMOs (MB-MIMOs) using only one single array beamformer. Time-modulated arrays (TMAs) introduce time as an additional degree of freedom to concurrently sample and multiplex multiple received signals in various incident angles. In other words, time modulation on the RX array enables spatial-spectral mapping that maps received information in different directions to different frequency components in received spectrum with crossbeam isolation, which can be de-modulated by downstream circuits. Thus, the proposed TM MB-MIMO RX array supports concurrent space division multiple access (SDMA) communication with only one beamformer. Furthermore, with built-in phase shifters, the TM MB-MIMO RX also achieves fast-beam scanning with low hardware complexity. A proof-of-concept 26–33 GHz TM MB-MIMO RX array is implemented in the GlobalFoundries 45 nm CMOS RF silicon on insulator (SOI). The demonstrated RX element shows $S_{11} < -10$ dB across 24–32 GHz, and its maximum conversion gain (CG) is 28 dB with a 3 dB bandwidth of 26–33 GHz. The measured noise figure (NF) is 5.78 dB at 28 GHz with RX input-referred IP $_{\mathrm {1\,dB}}$ of −38 dBm. The proposed RX supports wideband-16/64 QAM single carrier modulations with maximum modulation speeds of 2.4/4.2 Gb/s, respectively. The demonstrated MB-MIMO RX array achieves five concurrent beams with good crossbeam isolation using only four-element and one analog beamformer and supports wideband-16/64 QAM single carrier modulations on each beam.

I. Introduction

The rapidly growing use of mm-wave spectrum [1], [2], [3] for next-generation wireless systems has resulted in ubiquitous deployments of array-based systems due to their enhanced signal-to-noise ratio (SNR) and wireless link budget. To further increase the channel capacity and data rate, concurrent multibeam multiple-input- multiple-output (MB-MIMO) has become a promising direction to fully exploit the spatial diversity of mm-wave arrays.