Broadband Rf Power Amplifier Memory Effect

Since the number of users and broadband communication traffic rise rapidly, radio frequency resources are become more and more scarce. To enhance spectrum efficiency, linear modulation and multicarrier techniques are adopted widely in modern wireless communication systems, it deserves high linear radio frequency power amplifier (RF PA). Meanwhile, in order to solve the conflict between spectrum efficiency and power efficiency, external linearization techniques such as feedback,predistortion and feedforward are adopted widely. However, there are some differences between the practice results and the theory forecasts because of memory effects.The paper includes theory analysis of memory effects in the wideband RF PA and measurements, and research that the intermodulation (IM) changes with the various conditions change, especially with the various signals. The contents of the paper are as follows:1. The main nonlinear characteristics of RF power amplifiers and several basic modeling theories are described, and points out these models aren't suitable for wideband models.2. The definition of the memory effects in RF PA are proposed, the definition of the electrical memory effects and thermal memory effects are proposed based on the SPICE modeling of the RF PA. Meanwhile, the amplitude of signal will cause memory effects by means of fifth-order analysis.3. The intermodulation mechanism are deeply analysis by means of Volterra model, and get the information that each nonlinearity contributed to IM3, it is possible for internal linearization by means of these analysis.4. Several linearization techniques and how to simulate memory effects are proposed, the figure"Normalized IM3 Components"are proposed, meanwhile, the test setup and calibration for measuring memory effects are discussed.5. Three techniques to cancel memory effects are proposed, Impedance Optimization,Envelope Filtering,Envelope Injection, then discuss their differences and simulation results are listed .