Precisely Synchronized NVNA Setup for Digital Modulation Signal Measurements at Millimeter-wave Test Bands
This paper presents a novel NVNA setup for characterizing digital modulation signal at millimeter-wave bands. The first difference between this setup and commercial NVNAs is the use of a user-defined multisine signal as the phase reference, in order to enable more precise synchronization and denser spectral grid. To achieve this, a single 12.5-GHz microwave source is used not only to trigger the AWG for user-defined IF waveform generation, but also to provide the LO drive after frequency multiplication. The second novelty of this work is the use of pulsed-RF signals for NVNA phase calibration, so that tone-by-tone phase calibration on a dense spectral grid of 500 kHz can be easily achieved without any modification of the precisely-synchronized NVNA setup. According to the experimental verification at 28 GHz, the errors of NVNA phase calibration are less than ±2 deg., and the measured EVM of a 100-MSymbol/s 64-QAM test signal is 2.2%.