Over the past few years, there has been a growing need for wireless communications with higher data rates and ubiquitous coverage, and these must be achieved at
reduced cost and with a lower carbon footprint. This evolution in wireless demand places a big burden on transmitter architectures. The need for higher efficiency has stimulated research into the potential replacement of current linear power amplifiers (PAs) by switch mode power amplifiers (SMPAs) at cellular frequencies. The radio
frequency (RF) PA currently accounts for a significant part of the cost, and most of the power requirements of a typical wireless base station.

This research is focused on the modulation and up-conversion circuits for generating the SMPA drive signals. The switched (‘on’/‘off’) nature of the amplifier drive
signal creates an opportunity for an all-digital solution removing traditional analog components such as the digital to analog converters, reconstruction filters, quadrature
modulator and local oscillators. Digital signal processing techniques used for signal modulation are extended to digital up-conversion to generate suitable drive signals for the SMPA. In this thesis, a sigma-delta (ΣΔ) based technique is used to embed a complex modulation scheme such as OFDM into a single ‘on’-‘off’ bit stream.