Microwave measurements - Part III: Advanced non-linear measurements

This work completes the sequence started with articles [1] and [2], previously published in this journal, which presented the most important aspects of RF and microwave linear and non-linear measurements. In [1], some off-the-shelf linear measurement approaches at microwaves were described, whereas [2] showed the conventional characterization of non-linear devices under large-signal conditions, such as active and passive load-pull at fundamental and harmonic frequencies. In basic load-pull systems, the device under test (DUT) is driven by a single tone microwave source while the DUT performance metrics, typically output power and power added effi ciency (PAE), are monitored as a function of the load and/or source terminations. This strategy enables the straight-forward identifi cation of the optimum input and output loads. In this article, we describe two of the most advanced measurement techniques that can provide the required information for power amplifi er design and transistor modeling. The first technique is the multi-tone/complex modulation load-pull. It is useful especially for wireless applications, where conventional single tone excitations do not give suffi cient information for model and design development. The measurement conditions would be too far from the typical working ones. The second measurement technique is the timedomain waveform load-pull. Its applications span from highly accurate and reliable device model extraction to monitoring of actual operating conditions and "waveform engineering" for high-performance design.