Research On RF Power Nonlinearity And Mobile Communication Key Techniques

The key technologies for next generation and applications of the 3rd generation mobile communication have been the hot spot for current mobile communication research. This thesis focuses on some key techniques of nonlinear modeling and linearization for RF power amplifiers, and on some other key techniques about CDMA mobile communication.Aimed at RF high power amplifier's nonlinear characteristics, this thesis presents three memoriless models: the Saleh function based orthogonal bandpass model (Model A) converts the AM-AM and AM-PM distortions to two orthogonal I and Q channels that have only AM-AM distortion;the inverse tangent function based nonlinear model (Model B) describes HPA's nonlinearity by four parameters whose physical meanings are obvious;combined Model B with orthogonal bandpass model, Model C can deal with both the AM-AM and AM-PM distortions, and it gives the best performance among the three models.Based on the model research, this thesis presents two new adaptive linearization algorithms for memoriless power amplifier, theoretical analysis and emulation are also included. Ellipsic adaptive algorithm improves the linearity of the predistorted nonlinear power amplifier system and meets the real-time operation requirement;it is a better choise then the classic Newton's method or the gradient method. The adaptive algorithm based on circle work function speeds up parameters convergence, and it works better around the 1dB compression point.Mobile communication system using CDMA or OFDM technique needs a broader bandwidth for transmission, but the predistorter designed according to power amplifier's memoriless nonlinear model can only improve the IMD in a limit range. Based on the uniformly distributed time delay predistorter, this thesis presents an exponentially distributed time delay predistorter, emulation show that the new predistorter can depresss power amplifier's IMD deeper.Some key techniques in CDMA communication system, such as the ascertainment of long code state, the design of form filter, the coherent demodulation technique, are also included in this thesis. The new idea of binary expansion and some useful solutions arc offered. By using some extra memory to store state parameters, the time needed to ascertain long code state is greatly saved: by setting up an appreciate LUT. the number of operations for form filter could be two order smaller;by multiplying Hadama Transformer's time clock to N times the complex correlator's output data clock, one Hadama Transformer could be shared by N signals in time division mode. All these techniques are realized in the '"High-Speed CDMA BTS Demo System".Using the communication simulation tool SystemView by Elanix, the reverse channal close-loop power control technique in CDMA2000 system is modeled, and system's anti-jamming ability is studied.Three phase factor searching algorithms in PTS-OFDM system are discussed and emulated. A new approach is offered: in PTS-OFDM system, the auxiliary information can be modulated by the Gold sequence. Feasibility of the new approach is theoretically demonstrated, and MATLAB emulation shows that the new approach is acceptable.