Practical considerations for high-power X-parameter measurements for power amplifier design

This paper presents a measurement system that is capable of characterizing and modeling high-power (>;250W) RF devices outside the standard 50Q environment. The system is based on the Agilent PNA-X and Nonlinear Vector Network Analyzer (NVNA) measurement platforms. It is configured for measurements on a commercially available 250W average output power Lateral Diffused Metal Oxide Semiconductor (LDMOS) technology power transistor from NXP. A number of practical considerations are described in the paper such as setup of the PNA-X pulse generators and RF modulators to provide adequate pulsed measurement conditions, NVNA power budget calculations to sustain PNA-X measurement receiver linearity requirements, and configuration of accurate in-pulse drain current measurements to ensure proper transistor drain efficiency calculations. Procedures for performing accurate high-power vector and NVNA phase and amplitude calibrations are also described as well as source-and load-pull measurement results and X-parameter modeling results on the 250W LDMOS power transistor.