The Design Of RF Power Amplifier Based On Feedforward Systems And Predistortion

With the development of the wireless communication and the3G mobilecommunication, in order to solve the problem of increasing narrow communicationbandwidth, and low utilization rate of traditional spectrum constant envelopemodulation technology has been unable to meet the requirements of modernhigh-speed communications. People quadrature amplitude modulation (64QAM),quadrature phase shift keying (QPSK) and linear modulation technique modulationsignal through the non-linear amplifier can cause severe nonlinear distortion.Therefore, the RF power amplifier linearization techniques in recent years becomea hot topic of research at home and abroad.This thesis introduces the domestic and international power amplifierlinearization technology research and the current stats of the basic principles of thevarious linearization techniques, the basic theory of RF, including the transmissionline, two-port network, S-parameters, impedance matching and microstrip lines.Application of the Taylor series model, introduced power amplifier parameters ofnon-linear and the AM-AM and AM-PM conversion effects. Combinate the mathematical models of feedforward technology and pre-distortion technology, thevarious components of the feed-forward system are discussed in detail, as well aspre-distortion signal amplitude and phase conditions to be met the feedforwardsystem and pre-distortion design provides a theoretical supported. The transmissionline transformer on the main power amplifier impedance matching to solve theproblem of balanced end to tend signal transmission of non-equilibrium, while theuse of the four reactor auxiliary power amplifier impedance matching, reducing thereflected power of the port, improve the efficiency of power transmission.Pre-distortion system, splitters, couplers, attenuators, phase modulation and delayunits was simulated. Final design to meet the actual requirements of the RF poweramplifier system based on the feedforward and pre-distortion technology, theresults show that between the operating frequency88-108MHz, the system poweris greater than50dBm, The third-order intermodulation coefficient is less than-65dBc.