Millimeter-Wave Reconfigurable Adaptive Hybrid Beamformers for MIMO Communication

Millimeter-wave multi-input-multi-output (MIMO) communication, based on beamforming, is a revolutionary new element in wireless systems including 5G/beyond-

5G cellular, WiFi, radar etc. Highly integrated beamforming transceivers supporting basic directional communication through beam-steering, thereby improving the link-budget are reaching maturity. However, to further enhance the data rates and network capacity, advanced multi-antenna spatial signal processing techniques will be necessary in future wireless systems. This research introduces several systemic, architectural and circuit techniques that enable advanced spatial processing. Several millimeter-wave prototype chips implementing “hybrid beamforming” have been designed. Characterization of these prototypes conducted in lab and on-air settings showcase the mentioned techniques while achieving excellent system energy efficiency. This dissertation makes the following seven key contributions: 1) It introduces a “fully-connected” hybrid MIMO/beamforming architecture. Circuit architectures

and design techniques are introduced to implement RF-domain spatio-temporal signal processing, and in turn, facilitate a compact, energy-efficient and spectrally efficient

embodiment. 2) The fully-connected hybrid architecture is extended to enable reconfiguration across multiple MIMO modes in disparate mm-wave frequency bands (e.g., 28/37 GHz), and an inter-band full-aperture carrier aggregation

(CA) mode. 3) Beam adaptation techniques that enable adaptive beam and null formation in hybrid beamformers and RF phased arrays are introduced. Onchip implementations using a new time-multiplexed least mean square scheme are described. 4) A fundamental challenge in MIMO transmitter design due to the increase in peak-to-average-power-ratio is studied. The system energy efficiencies of several hybrid MIMO architectures across various power amplifier topologies are compared rigorously via analysis and experiment. 5) A new architecture is introduced that directly enables simultaneous transmit and receive (STAR) beamforming for multi-antenna frequency-division-duplexing (FDD) or full-duplex (FD) communication

with a per-element self-interference cancellation scheme. 6) Hybrid MIMO architectures with multi-layer spatial signal processing that mitigate complexity versus spectral-efficiency tradeoffs of single-layer hybrid beamforming architectures are proposed; in addition, these architectures facilitate efficient upward scaling of the number of supported MIMO streams and users. 7) A compact, bidirectional

transceiver architecture and constituent circuit techniques are proposed which enable dual-band transceiver operation. These techniques allow the transceiver to be reconfigurable

between numerous transmit/receive configurations that combine MIMO, CA, TDD, FDD and FD functionalities.