VNA-Based Large-Signal Characterization of Electronic Devices at Sub-mm-Wave Frequencies

As the number of wireless applications increases every year, overcrowding the RF/microwave spectrum, research community and industry are gradually starting to dedicate more attention to the less exploited (sub)mm-wave spectrum, spanning from 30GHz to 1THz. While the high frequency and large available bandwidth of the latter promises very fast communication and the space for countless new applications, the development of new devices working at high frequency is hampered by a series of challenges affecting both technology development and implementation. One of the bottlenecks in new technology development is the availability of accurate and reliable measurement techniques, to support the design and the model validation of active devices working at (sub)mm-wave frequencies. As a matter of fact, the test and measurement market dedicated to sub-THz applications has presented small developments in the last decades, with the core instrumentation and measurement techniques still based on the same principles dedicated to lower frequency applications. In this presentation, we will explore the main challenges related to large-signal characterization of transistors and PAs at frequencies higher than 70GHz, we will analyze the limitations associated to conventional instrumentation, especially in relation to load-pull measurements, and then describe alternative solutions, based on active injection and the use of VNA-based setups, to try to overcome those limitations.