Active Tunable Millimeter-wave Reflective Surface across 57-64 GHz for Blockage Mitigation and Physical Layer Security

Millimeter-wave wireless networks allow for spatial multiplexing and high throughput. However, they are critically susceptible to blockages, channel propagation variations, and fading. To incorporate resilience in such networks, a class of reconfigurable surfaces realized with reflect-arrays have shown theoretical promise in reconfiguring the channel on demand, creating programmable non-line-of-sight (NLOS) paths, and providing a scalable solution compared to densification of base stations and access points. In this paper, we present a scalable approach towards realizing active surfaces with the ability to simultaneously receive, amplify, beamform, and re-transmit to the intended receiver (Rx) in a secure fashion. We demonstrate with the proof-of-concept 2D and 1D arrays realized with custom silicon ICs in a 65-nm CMOS process while the reception and re-transmission is achieved through off-chip packaged dual-feed probe-fed patch antenna. Each chip incorporates two independent transceiver (TxRx) chains, with two-stage LNA and a 5-bit controlled 360° IQ phase shifter, collectively providing controllable gain of up to 15.2dB, P sat of 4.2dBm at 60GHz, noise figure ≈ 5–6dB, and supporting up to 20Gbps with 32-QAM constellation. With packaged 1D and 2D arrays, we demonstrate ±45° beamforming capability for various Tx positions closing links where simple reflective surfaces tend to fail. In addition, with spatio-temporal control over the surface, we also demonstrate physical layer security.