Dynamic Range by Design in OTA EVM Measurements

We present an experimental approach to design an over-the-air (OTA) millimeter-wave system for measuring error vector magnitude (EVM) with associated uncertainties that include correlations and nonlinearities. Our approach uses a variable waveguide attenuator at the output of a modulated-signal source at 44 GHz and provides traceable measurements on a calibrated equivalent-time sampling oscilloscope. The conductor-based EVM measurements and associated uncertainties presented here serve as a baseline for the eventual OTA-based EVM. We also discuss a noise based EVM estimation technique as a simple tool for planning OTA EVM measurements, but without a complete knowledge of measurement uncertainties.