IN WIRELESS communications, many count on power-amplifier (PA) efficiency for energy savings. At the same time, wireless communications demands a multi-mode PA, as the base station must be compatible with different standards. To meet these needs, a compact, concurrent, dual-mode PA has been created by Wenhua Chen, Xiang Li, Li Wang, Zhijun Zhang, and Zhenghe Feng at Tsinghua University. At its roots are a stub-tapped transformer and compensation inductance, which enable a dual-band output-matching network.

The researchers opted to use a silicon-carbide (SiC) MESFET as the active device in this design. An experimental device provided output power levels of +38.1 and +38.6 dBm with drain efficiencies of 63.4% and 65.1%, respectively, at 920 and 1200 MHz. Because this approach is not limited by the ratio of two designed frequencies, it can be extended to other applications. See "A Novel Concurrent Dual-Mode Class-E PA Using Dual-Band Stub Tapped Transformer," Microwave And Optical Technology Letters, Jan. 2011, p. 171.