Medium power-wideband envelope tracking RF power amplifier design

Thesis Type: Postgraduate

Institution Of The Thesis: Orta Doğu Teknik Üniversitesi, Faculty of Engineering, Department of Electrical and Electronics Engineering, Turkey

Approval Date: 2015


Supervisor: ŞİMŞEK DEMİR


An inevitable trade-off between efficiency and linearity challenges RF researchers more than ever in today’s wireless communication systems. The reason is the tight linearity requirements of the high peak-to-average power ratio (PAPR) signals. Linearity is crucial because modern communication systems transmit non-constant envelope modulation signals. Efficiency is also crucial because portable systems have limited source of power and dissipated heat power increases cooling system cost. Various power amplifier architectures have been demonstrated to achieve high efficiency for high PAPR signals. One of them has different property. This one is fundamentally immune to changes in the frequency of the carrier; it depends only on the envelope of the RF signal. This dissertation focuses on the design of Envelope Tracking Power Amplifier (ETPA) for enabling broadband wireless communication with high efficiency. First, load and supply modulation techniques are reviewed. In second chapter, main blocks of ETPA are described and efficiency formulas are given. Then, 10W LDMOS RFPA is designed with the help of CAD programs and implemented on the PCB. In third chapter, hybrid envelope amplifier topology is introduced to maximize efficiency for large back-offs and implemented on the PCB. Finally, ET system is tested with 5 MHz-WCDMA with 9.7 dB PAPR. Drain efficiency and ACPR measurements are tabulated. To better understand the ET operation, simulations with ADS are done. Comparison table of constant supply voltage RFPA and ET PA is added to show the efficiency enhancement.