Multilevel converter for Envelope Tracking in RF power amplifiers

Envelope Tracking techniques are used to increase the efficiency of modern radiofrequency transmitters. These techniques are based on varying the supply voltage of the amplifiers according to the envelope of the signal being transmitted, thus maximizing their efficiency. Converters suitable for Envelope Tracking applications must provide high tracking bandwidths, along with low output voltage ripple. This paper presents a power supply for Envelope Tracking applications based on a multilevel topology: it targets relatively low voltage systems (12–28 volt range) and medium to high power applications (≫ 50 W peak power). It uses several input voltages to generate a multilevel square waveform which can be easily filtered; it achieves low output voltage ripple, high tracking bandwidths, high efficiency and high output power capabilities. This paper first analyzes its steady-state behaviour; then, a design procedure is provided, along with guidelines for appropriate implementation of the proposed system. A three-level prototype was built to test the system, and its performance is shown in the experimental results section. Finally, conclusions are stated.

[1]  Pedro Alou,et al.  Multilevel Power Supply for High-Efficiency RF Amplifiers , 2009, IEEE Transactions on Power Electronics.

[2]  R. Madhusudhanan,et al.  FPGA based Digital Pulse Width Modulator with Time Resolution under 2 ns , 2009 .

[3]  Javier Sebastian,et al.  High-efficiency and wide-bandwidth performance obtainable from a two-input buck converter , 1998 .

[4]  M.A.E. Andersen,et al.  High-Bandwidth, High-Efficiency Envelope Tracking Power Supply for 40W RF Power Amplifier Using Paralleled Bandpass Current Sources , 2005, 2005 IEEE 36th Power Electronics Specialists Conference.

[5]  V. Yousefzadeh,et al.  Three-level buck converter for envelope tracking applications , 2006, IEEE Transactions on Power Electronics.

[6]  Benjamin C. Kuo,et al.  AUTOMATIC CONTROL SYSTEMS , 1962, Universum:Technical sciences.

[7]  L.E. Larson,et al.  Design of wide-bandwidth envelope-tracking power amplifiers for OFDM applications , 2005, IEEE Transactions on Microwave Theory and Techniques.

[8]  Alberto Rodriguez,et al.  Analysis of the switching process of power MOSFETs using a new analytical losses model , 2009, 2009 IEEE Energy Conversion Congress and Exposition.

[9]  A.P. Chandrakasan,et al.  Ultra low power control circuits for PWM converters , 1997, PESC97. Record 28th Annual IEEE Power Electronics Specialists Conference. Formerly Power Conditioning Specialists Conference 1970-71. Power Processing and Electronic Specialists Conference 1972.

[10]  D.R. Anderson,et al.  High-efficiency high-level modulator for use in dynamic envelope tracking CDMA RF power amplifiers , 2001, 2001 IEEE MTT-S International Microwave Sympsoium Digest (Cat. No.01CH37157).

[11]  M.A.E. Andersen,et al.  Self-oscillating soft switching envelope tracking power supply for Tetra2 base station , 2007, INTELEC 07 - 29th International Telecommunications Energy Conference.

[12]  J.A. Cobos,et al.  Power supply for a radio transmitter with modulated supply voltage , 2004, Nineteenth Annual IEEE Applied Power Electronics Conference and Exposition, 2004. APEC '04..