Comparison of Residual EVMs in Modulated-signal OTA Tests using VNA- and VSA-based Approaches

In this paper, the performance of error vector magnitude (EVM) is compared between a commercial vector signal analyzer (VSA) and VNA-based test bench designed by us. Furthermore, the influence of different receive and transmit antenna distances on the measurement results is explored. It has been found that the residual EVM of the VNA-based test bench is significantly lower than those of the commercial VSA at various distances. This is achieved through the pre-distortion of the VNA at the receiver. Typically, the residual EVM of the VNA measurement system is 0.41%, while the VSA is 4.35% at a distance of 400 mm. This paper presents experimental verification of the effectiveness and superiority of the proposed VNA-based test bench.