Extension of NVNA Baseband Measurement for PA Characterization Under Complex Modulation

—We investigated the measurement techniques of thenonlinear vector network analyzer (NVNA) test bench, to fullycharacterize the nonlinear behavior of radio frequency (RF)power amplifiers (PAs) driven by complex modulated signals.In order to extend the baseband measurements, two kinds ofNVNA phase reference approaches are developed as alternativesolutions, so that the baseband phase measurements can beachieved with those of modulated components at multiharmonicRF bands. In the first approach, a modulated baseband signalis combined with another modulated RF one to become thedesired NVNA phase reference. While as an alternative solution,the second phase reference design is based on a “stepped”multisine, which is stepped through the baseband and eachharmonic following the NVNA swept measurements, to achievestable phase measurements. To validate these proposed NVNAtest bench designs, an RF PA, driven by a large-signal long-termevolution-like multisine, was tested and compared with digitalreal-time oscilloscope measurements.