The digital power amplifier for the wireless infrastructure: Status and prospects

In digital power amplifiers the analog signal is not handled directly but encoded in a pulse train. It is restored only at the output by a bandpass filter. Due to the discretization in amplitude, this principle, often referred to as class S, allows for efficient and versatile amplifiers. While in widespread use for audio frequencies, digital PAs have been introduced at microwave frequencies only a few years ago. The paper reviews the state of the art of such PAs for applications in the wireless infrastructure. The key factors determining transmitter performance are addressed and recent results are presented.