Analysis and Optimization of Transformer-Based Power Combining for Back-Off Efficiency Enhancement

作者：Kaymaksut Ercan^*; Francois Brecht; Reynaert Patrick

来源：IEEE Transactions on Circuits and Systems I-Regular Papers, 2013, 60(4): 825-835.

DOI：10.1109/TCSI.2012.2221223

• Back-off efficiency
• CMOS technology
• Doherty power amplifier
• series combining transformer

This paper analyzes the back-off efficiency enhancement characteristics of transformer combined power amplifiers taking into account the amplifier and transformer parasitics. The dynamic power combining properties of different transformer architectures are investigated. The co-optimization of the transformer and the amplifiers is presented for the transformer-based Doherty power amplifier which is a linear class of operation with back-off efficiency enhancement. Then this analysis is extended for the uneven Doherty power amplifier which employs asymmetrical transformers. The proposed design methodology is used to design a 2.4 GHz uneven Doherty power amplifier in standard 90 nm CMOS technology. The fabricated two stage Doherty amplifier achieves 26.2 dBm peak output power at 2 V supply. The measured peak drain efficiency of the PA is 37% while the efficiency at 6 dB back-off is still as high as 30.1%.

• 出版日期2013-4