4.4 A 28/37GHz Scalable, Reconfigurable Multi-Layer Hybrid/Digital MIMO Transceiver for TDD/FDD and Full-Duplex Communication
Susnata Mondal, L.R. Carley, Jeyanandh Paramesh
Abstract
This paper describes an advanced mm-wave MIMO transceiver with several innovative attributes. It introduces a multi-layer hybrid/digital MIMO architecture that comprises multiple tiles having fully connected (FC) RF-domain complex-weights in the first layer, followed by fully connected (analog or digital) baseband layer(s). This architecture mitigates complexity versus spectral-efficiency tradeoffs of hybrid MIMO architectures (Fig. 4.4.1), and enables efficient upward scaling in the number of MIMO streams. The architecture can be configured into numerous multi-layer hybrid MIMO modes comprising FC or partially-connected (PC) RF tiles, or as the front-end of a fully digital MIMO array, or as a conventional phased-array [1]. Another important contribution of this paper is the demonstration of full-duplex (FD) multi-antenna communication, enabled by on-chip self-interference cancellation (SIC). In the RX path, the MIMO transceiver features three-step successive SIC with a per-element SIC step that cancels TX leakage in the RF domain independently for each element. It is important to note that such SIC is available only with tiles that have FC in the first layer. To realize autonomous SIC, an on-chip adaptation engine is implemented that optimally sets SIC weights for each element using a time-multiplexed least-mean square (LMS) algorithm.