New Ultra-fast Real-time Active Load-pull Measurements for High Speed RF Power Amplifier Design

To accelerate the speed of RF power amplifier design, a novel ultra-fast real-time active load-pull measurement based on a large signal network analyzer (LSNA) is presented. Real-time load-pull conventionally uses a single-tone excitation at the transistor´s output to achieve a time varying load impedance. However this approach still requires multiple measurements at different power levels to map the Smith Chart and determine the optimal load termination. This paper proposes a modulated two-tone excitation method for mapping the Smith Chart in a single 10 ms LSNA measurement. Experiments for the l^st and 2^nd harmonic demonstrate that this ultra-fast real-time active load-pull permits to identify the optimal load impedance in one measurement.