Radio frequency carrier amplitude-burst transmitters – from architecture to circuit

The radio frequency carrier amplitude-burst transmitter constitutes a promising architecture capable of efficiently transmitting signals of highly demanding complex modulation schemes. However, the tested practical implementations present results that stay way behind the theoretically advanced promises. This study presents the first thorough study of the power efficiency and linearity characteristics that can be actually achieved with this architecture. The analysis starts with a brief revision of the theoretical idealised behaviour of these switched-mode amplifier systems, followed by the study of the many sources of impairments that appear in their real implementation. In particular, a special attention is paid to the dynamic load modulation caused by the often ignored interaction between the narrow-band signal reconstruction filter and the switched-mode power amplifier. The performance of this architecture is clearly explained based on the presented theory, which is supported by simulations and corresponding measurement results of a fully working implementation. The drawn conclusions allowed the development of a set of design rules for future improvements.