Proof-of-Concept of Millimeter-Wave RF Beamforming Transmitter Architecture Employing Frequency-Multiplier-Based Up-Converters

This letter proposes a millimeter-wave (mm-wave) RF beamforming transmitter (TX) architecture that employs frequency multipliers (FMs) as frequency up-converters to avoid the challenges associated with the signal and local oscillator (LO) distribution networks that intensify with the increase of operating frequency. The proposed architecture incorporates a single-input- single-output (SISO) digital predistortion (DPD) scheme that is specifically devised to mitigate the nonlinear distortions exhibited by the cascade of FMs and power amplifiers (PAs). Proof-of-concept experiments conducted on a lineup, comprised of an off-the-shelf frequency doubler and an 8x 8 array and operating at an output frequency of 28 GHz, confirmed the capacity of the proposed architecture to transmit 200 MHz orthogonal frequency division multiplexing (OFDM) signals with an error vector magnitude (EVM) and adjacent channel power ratio (ACPR) better than 1.6% and 45 dB, respectively, while achieving an effective isotropic radiated power (EIRP) of 46.3 dBm.