This document relates to the TRF370x direct quadrature modulator for applications in the transmit path of base stations and communications equipment. The quadrature modulator is used for upconversion of signals from the transmit chain DAC to the RF power amplifier device. Evaluating modulator complex performance involves careful bias-voltage setup, an LO signal, and two differential (I/Q) signals at the input of the modulator. This document describes the wide range of test options available and the factors that must be considered in using this EVM