Linearization of mm-Wave Large-Scale Phased Arrays Using Near-Field Coupling Feedback for >10Gb/s Wireless Communication

This paper proposes a digital predistortion (DPD) technique for power amplifiers (PAs) in a large-scale multi-tile millimeter-wave (mm-wave) TX/RX phased-array system. By utilizing the nearfield coupling feedback between TX and RX elements for observation, the proposed DPD can linearize the main beam of a transmitted signal over the range of possible steering angles without the need for any additional dedicated far-field DPD observation circuitry or hardware. The proposed DPD is evaluated by linearizing a 256-TX and 128-RX element array driven by a 2.5-GBaud 16/64-QAM signal centered at 90 GHz. A single set of DPD coefficients achieve up to 8.8-dB improvement in Noise Power Ratio (NPR) as well as up to 5.6-dB improvement in Adjacent Channel Power Ratio (ACPR) across the 120° azimuth and 100° elevation steering range of the antenna array. Wireless links also demonstrate EVM improvements of up to 5.1 dB at 10 Gb/s.