Verification of Real-Time Oscilloscope for Millimeter-Wave Modulated-Signal Measurements Using an NVNA Test Bench

In this article, a nonlinear vector network analyzer (NVNA)-like measurement setup is developed to characterize millimeter-wave digitally modulated signals with low error vector magnitude (EVM) in the frequency domain, which is later used to verify the performance of a commercial high-speed real-time oscilloscope (RTO) for vector signal analysis. To accomplish that, a frequency-domain predistortion method is used to lower the EVMs of 64-state quadrature amplitude modulation (64-QAM) test targets with carrier frequencies from 20 to 42 GHz and symbol rates from 0.1 to 1 GSymbol/s. According to the method validation typically at 28 GHz with a symbol rate of 0.5 GSymbol/s, the proposed NVNA setup can derive the low-EVM measurements of 0.29% with an upper 95% confidence bound of 0.85%. The RTO measurement of the same signal is up to 2.02%, which is codetermined by the in-band RTO responses and an EVM floor of 1.47%.