Analysis Of The Power Amplifier Memory Effects, Measurement, Simulation And Calibration

Radio frequency power amplifier is an important module of mobile communication system; as well a unit which consumes most of the energy of base station, therefore the cost of a wireless communication system network's construction and operation is directly depended on the power amplifier's efficiency. But, the contradiction between efficiency and linearity of the power amplifier is more and more violent, especially in the third generation mobile communication technology. Non-constant envelope modulation and multi-carrier technology are widely used to improve the spectrum efficiency in the third generation mobile communication, which requires more stringent linearity of power amplifier. In addition to optimizing the design of power amplifier itself, some linearization techniques have been widely used, such as negative feedback, feedforward and pre-distortion. However, mainly due to the existence of memory effects in power amplifier, these linearization techniques always can't reach the desired results.In this paper, the generation mechanism of the memory effects in power amplifier is analyzed, the changes of nonlinear distortion components affected by memory effects are studied, and a method to reduce the thermal memory effects is proposed by means of simulation. The contents of the paper are as follows:1. The nonlinear characteristics of RF power amplifiers and some linearization techniques are described, and these linearization techniques are compared from the perspective of memory effects.2. Since the definition of the memory effects in RF power amplifier is givened, the memory effects are classified by means of deep analysis of its generation mechanism, finally the external behaving of memory effects is pointed out.3. The physical and behavioral modeling of power amplifier are described, then thermal and electrical memory effects of LDMOS FET and power amplifier are simulated based on physical modeling, and the changes of nonlinear distortion components affected by memory effects are analyzed.4. The methods how to eliminate the thermal and electrical memory effects are described, a temperature compensation feedback circuit is proposed to eliminate the thermal memory effects.