Simple and low-cost tracking generator design in envelope tracking radio frequency power amplifier system for WCDMA applications

• Published in: IET microwaves, antennas & propagation antennas & propagation, 2013-07, Vol.7 (10), p.802-808
• Main Authors: Yusoff, Zubaida, Lees, Jonathan, Chaudhary, Muhammad Akmal, Carrubba, Vincenzo, Choi, Heungjae, Tasker, Paul, Cripps, Steve C
• Format: Article
• Language: English
• Subjects: AC component; AET signal tracking; amplified envelope signal; Amplifiers; Applied sciences; auxiliary envelope tracking; Broadband; Circuit properties; code division multiple access; DC component; Design engineering; drain efficiency; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Envelopes; Exact sciences and technology; gallium compounds; GaN; Generators; III‐V semiconductors; Microwave antennas; noise figure 9.17 dB; peak‐to‐average envelope power ratio; power 25 W; Power amplifiers; Radio frequencies; radiofrequency amplifiers; radiofrequency power amplifier system; RF broadband transformer; RFPA; simple analogue technique; simple source follower amplifier; target tracking; Tracking; tracking generator design; transformers; WCDMA application; wide band gap semiconductors; wideband amplifiers
• ISSN: 1751-8725; 1751-8733; 1751-8733
• DOI: 10.1049/iet-map.2013.0091

A simple analogue technique called auxiliary envelope tracking, or AET, is presented, which is shown to be capable of improving the efficiency of a radio frequency power amplifier (RFPA). This AET signal is an amplified envelope signal that supplies the drain port of the RFPA. The concept of AET is explained and a theoretical background for the technique is presented. The main feature of this technique lies in the separation of the DC and AC components of the tracking signal. This allows for a very simple and low-cost tracking generator design that consists of a simple source follower amplifier and an RF broadband transformer. A practical system has been implemented and the measured results are obtained for WCDMA signals. A measurement on the realised system shows a 50% improvement in the drain efficiency at average output power of 33 dBm of a 25 W GaN. This substantial improvement is achieved at a competitive WCDMA signal with peak-to-average envelope power ratio of 9.17 dB.