Waveform engineering applied to linear-efficient PA design

Low-frequency, baseband effects in Power Amplifiers can become particularly important when steps are taken to improve operational efficiency through the application of ‘envelope’ based approaches such as Envelope Elimination and Restoration (EER) and Envelope Tracking (ET). The aim of this paper is to demonstrate how a broadband modulated time-domain measurement system, when used in combination with active IF load-pull, can be employed to gain valuable insight into the behaviour of high-frequency power transistors whilst operating under modulated conditions. Also considered is the interesting idea of how PA linearity can be improved using the very mechanisms that are employed to improve efficiency.