High-Frequency Vector-Modulated Signal Generation Using Frequency-Multiplier-Based RF Beamforming Architecture

In this paper, a frequency-multiplier-based radio frequency (RF) beamforming architecture suitable for the generation/transmission of high-frequency vector-modulated signals is proposed. The proposed architecture incorporates a single-input-single-output digital predistortion function that has been carefully synthesized to guarantee excellent error vector magnitude (EVM) and adjacent channel power ratio (ACPR) for the signals received in the far-field. A 2×2 beamforming array was built using off-the-shelf frequency doublers and printed circuit board based patch antennas, all operating at 28 GHz, to serve as the device-under-test in the validation experiments. Over-the-air experiments confirmed the ability of the proposed architecture to successfully generate orthogonal frequency division multiplexed (OFDM) signals. For instance, EVMs as low as 0.9% and 2.5% and ACPRs equal to 52 dBc and 47 dBc, were obtained for modulation bandwidths equal to 100 MHz and 400 MHz, respectively.