Analysis, modelling and linearization of nonlinearity and memory effects in power amplifiers used for microwave and mobile communications

The evolution in wireless technology, from voice-only service to advanced data-centric service, and also increasing number of mobile users, require increased system capability. Such improvement will increase the required bandwidth and power level of the system. Moreover, newer transmission formats, such as wideband code division multiple access (WCDMA) and orthogonal frequency division multiplexing (OFDM) with high peak to average power ratios, cause large variations in the signal envelope. In this case, the used power amplifier (PA) in the system should produce a high output power and it should be highly linear. The main objective of this thesis is to investigate the possible method(s) for modelling and linearization of broadband PAs with memory effects. The memory effects are envelope frequency dependent phenomena, which distort the amplifier output spectrum and limit the efficiency of linearization methods. Consequently, these effects present big challenge in today’s wireless mobile communication and microwave applications, in which digital modulation schemes with non-constant envelope are used. To achieve linearized broadband PA, the memory effects should be analyzed, characterized and modelled.