A load-pull technique for the determination of transistor S parameters under large-signal conditions

A novel method is presented for determining the large single S parameters of transistors under drive conditions using data obtained from load-pull measurements. The technique uses a load which can have a variable amplitude and phase, and can thus control the amplitude and phase of the signal at the device output. A mathematical analysis of the method is presented and typical results for the large-signal S parameters of an X-band FET are given. The gain compression and AM/PM conversion limits of a linearized power amplifier are then calculated.