Abstract

In this thesis, adaptive polynomial predistortion techniques suitable for DSP implementation at the baseband signals are introduced to counter-balance the AM/AM and AM/PM nonlinear effects of the transmit power amplifier. The proposed polynomial predistortion scheme is based on polar coordinate representation. Both LMS and RLS concepts are used to derive the adaptive algorithms. An enhanced LMS-based algorithm with fast convergence is proposed. For very fast convergence, a cascaded RLS-based adaptive polynomial predistorter structure is introduced. The obtained results show that the polynomial predistortion schemes can be used in M-QAM transmitters with power amplifiers operating near saturation to achieve a highest power efficiency. The thesis also presents a class of circular M-ary Amplitude-Phase Shift Keying (APK) signaling techniques with high bandwidth efficiency and low peak-to-average power ratio (PAR) suitable for systems using non-linear power amplifiers to achieve high power efficiency. Based on bandlimited two-dimensional M-ary signals using circular constellations, a search algorithm for optimum schemes for non-linear amplification in terms of minimum PAR and maximum DPR is introduced. Optimum circular constellations for 8-, 16-, 32-, 64- and 128-APK signalling schemes are proposed. The analytical and simulation results show that this class of circular M-ary APK signals outperforms the square and cross M-ary QAM schemes.