Study Of Feedforward Linearization Technology For RF Power Amplifier

For the sake of saving the frequency source, the fashion digital communication technologies always have the common characteristic of multi-carrier and high ratio of apex to average, which bring forward much more strict linearization target to the RF system. So the linearization technology for RF power amplifiers becomes one of the important items in the wireless communication theory. The feedforward technology has the best effect for linearization and becomes the most popular linearization technology.The characteristics of the nonlinear distortion and the principium of usual linearization technologies have been proposed during the chapter one to chapter three, and so the commons and differences between them.The chapter 4 first indicates that one of the important causes of amplitude-mismatch and phase-mismatch based on the traditional feedforward circuit is the main PA's echo. The effect on the amplitude and phase of bi-loops' feedforward circuit's error signal brought by the echo and some measures have been analyzed, thus the expressions of variations in amplitude and phase of the error signal against amplitude-mismatch and phase-mismatch have been proposed later. At last, a feedforward circuit against the echo has been designed to decrease the nonlinearization distortion effectively.At the chapter 5, the merits and disadvantages of the usual bi-loops adaptive feedforward circuit by decreasing the nonlinearity distortion and exporting enough power are discussed first. We introduce another feedforward circuit by coupling some signal from the input of the main power amplifier to the input and output of the auxiliary power amplifier to reduce more IM3 and increase the output power. The results show that the IM3 reaches below -75dBc, which is much more acceptable than before by 10dB, and the output power has increased by 2dB.