Evaluation of EVM Performance of Antenna System under Digitally Modulated OTA Scenarios

In this paper, we investigate the performance of millimeter-wave antennas under digitally modulated test scenarios, and propose a novel method to quantitatively evaluate the relative error vector magnitude (EVM) degradation when the orientation of antennas changes from the on-axis to the off-axis. To measure the relative deviations, a calibration-free vector network analyzer (VNA) based test bench is utilized in this work so that the tone-by-tone frequency-domain magnitude and phase changes can be obtained. Based on the measured distortions and the knowledge of ideal test stimulus, the off-axis EVMs can be determined from reconstructed waveforms when assuming the on-axis one is ideal. This method can circumvent the nonideality of millimeter-wave test stimuli when analyzing the performance of antenna system.