Pulsed S-parameter Measurements

Many devices, particularly power devices, were not designed to operate continuously or with CW signals. When devices are being tested on-wafer, this becomes even truer since thermal resistance is often greatly increased (e.g., [1]). In these cases, S-parameter measurements must often be performed in a pulsed environment. The details of the measurement are greatly dependent on the pulse properties being studied. At one extreme is the realm of high pulse repetition frequencies (PRFs) and fairly narrow pulses as is common in radar applications. At the other extreme is the communications arena where PRFs are quite low and pulse widths fairly wide (e.g., GSM [2]). These two extremes exemplify two techniques, termed bandwidth limited and triggered, that are discussed in this note. The two approaches overlap in terms of allowed parameters to a certain degree so most situations can be covered by one if not both of them. Pulse profiling of the detailed transient response is not covered here although it is briefly discussed with regard to triggered measurements elsewhere [3]. Certain rise/fall time behaviors can be studied using time domain mode [4] but that will not be discussed either. The objective is to gain an understanding of performing general S-parameter measurements with a vector network analyzer (VNA) across a range of pulsed conditions for both RF and microwave/mm-wave measurement applications.