Precision Millimeter-Wave-Modulated Wideband Source at 92.4 GHz as a Step Toward an Over-the-Air Reference

As the next-generation communications technology continues to evolve to utilize millimeter-wave frequencies, calibration methods are needed for the nonidealities related to these frequencies in communications electronics. In this article, we demonstrate a 1-GHz bandwidth, 64-quadrature-amplitude-modulated signal source at 92.4-GHz carrier frequency with relative phase and magnitude that may be made traceable to primary standards. By using predistortion techniques, we are able to repeatably obtain a nominal error vector magnitude (EVM) of 1.4%. In addition, we track correlated and uncorrelated uncertainties using a Monte Carlo method to show the distribution of uncertainty of the EVM measurement with the 5th and 95th percentiles at 1.5% and 3.1%, respectively. We examine the dependence of the EVM in the traceable source on digital-to-analog converters' imbalance and system drift over time. Finally, we use the stable, low-EVM signal to ascertain EVM degradation on- and off-axis in a stationary over-the-air setup.