Traditional amplification topologies use linear classes of power amplifiers (PAs) such as class A and class AB. Despite their good linearity performance, these classes are limited in power efficiency. Switching mode PAs have been proposed to reduce the energy dissipation by operating in two possible states, either ON or OFF providing 100% efficiency theoretically. To achieve this high efficiency a tuneable and low-loss matching network is required. In the present work, theoretical analysis of the harmonic output matching network losses is developed and applied to two different tuneable matching topologies. This analysis is adopted in the design of switching mode PAs to minimize the loss of its output matching circuit, which resulted in PAs with a state-of-the-art efficiency.

The designed switching mode PAs are used in advanced transmitters topologies such as linear amplification with nonlinear components (LINC) and delta-sigma (ΔΣ) transmitters. These architectures transform the amplitude and phase modulated signal in constant envelope signals, which can be amplified linearly and efficiently with switching mode PAs. However, the efficiency/linearity of the transmitter degrades after reconstructing the amplitude modulation of the signal.

Two new signal decomposition approaches based on mode-multiplexing (MM-LINC) technique are proposed to enhance the efficiency of LINC transmitters with isolated combiner. In the case of a non-isolated combiner, digital predistortion of the LINC transmitter is proposed to compensate for the nonlinearity introduced to the system.

Signal processing complexity is one of the major challenges in implementing delta-sigma-based transmitters. Two approaches are proposed to reduce the required baseband processing speed, which allows an implementation of the whole transmitter in digital domain making it suitable for multi-standard applications.