21.3 A Reconfigurable Bidirectional 28/37/39GHz Front-End Supporting MIMO-TDD, Carrier Aggregation TDD and FDD/Full-Duplex with Self-Interference Cancellation in Digital and Fully Connected Hybrid Beamformers

This paper presents a 28/37/39GHz front-end applicable to beyond-5G wireless networks. It features three key contributions. First, a fully connected (FC) transmitter architecture is introduced for hybrid beamforming (HBF); it is shown that the power efficiency of FC-HBF is superior to the conventional partially connected (PC) HBF for a given modulation and antenna geometry. Second, a compact/low-cost circuit concept is introduced that supports bi-directional T/R operation concurrently at 28 and 37/39GHz, thereby facilitating multi-antenna carrier-aggregation (CA) or MIMO TDD with high antenna count. Third, a built-in mechanism for dual-band, per antenna, self-interference cancellation (SIC) is introduced, thanks to the FC-HBF architecture. The front-end is applicable to FDD or full-duplex (FD) multi-antenna systems; such SIC is not available in PC-HBF's. Also, the front-end is directly applicable to dual-band digital beamformers (DBF).