Demystifying Device related Memory Effects using Waveform Engineering and Envelope Domain Analysis

Although memory-less pre-distortion together with memory mitigation techniques are used extensively in countering the effects of PA non-linearity, the sources of non-quasi-static non-linear behaviour are still not fully understood. In this paper, it is argued that some observations, generally considered to be evidence of `mysterious´ device memory effects have much more fundamental origins, such as simple linear delay or non-ideal impedance environments that vary over bandwidth. This paper presents detailed modulated measurements that aim to help clarify this problem and to isolate some of the contributors to what has now become a rather general `catch-all´ term of `memory effects´. The analysis is based on modulated (two-tone) waveform measurements and envelope analysis of both a simple passive line structure, as well as an active 2W GaN die operating at 2.1 GHz and over a bandwidth of 80 MHz.