DDS-based injected tone canceling method for short-wave PA memory effects measurement

In the PA modeling, phenomena such as asymmetries in inter modulation (IM) amplitude and phase is always applied to evaluate the power amplifier's (PA's) memory effects, and the phase measurement of nonlinear distortion component is very difficult. In this paper, we present the injected canceling method using direct digital synthesizer (DDS) to generate tested two-tone and injected tone which will be taken as a reference signal, as well as by canceling principle to measure the amplitude and phase of the nonlinear distortion components of DUT (device under test), and discuss the application conditions. For a 2000 W short-wave PA, we assess the memory effects according to the measured data by the proposed method. The advantages of this method include that the initial phase of the injected tone could meet the requirements of the memoryless polynomial model conveniently, due to the characteristics of DDS technology, and the calibration is simpler, moreover, the method is suitable for measuring other distortion components except IM3, comparing with the three-tone injected measurement proposed by Vuolevi. J.