A novel high effective envelope-tracking amplifier for OFDM systems

OFDM (orthogonal frequency division multiplex) mobile communication system is so popular in recent because it has so many virtues as effective frequency spectrum, wide-band, high speed rate, etc. But it has so many challenges in technical field, such as the high efficiency of PA (power amplifier) and linearity. RF (radio frequency) amplifier with ET (envelop-tracing) structure is described for OFDM systems in this paper. The first study the ET amplifier model, and then a high-efficiency OFDM amplifier is presented with GaN HEMT (heterostrucutre field-effect transistors), and includes the theoretic analysis and circuit design. Finally, the design circuit is simulated by ADS (advanced design systems) software, and gets the average DE (drains efficiency) of the amplifier is as high as 50% for an OFDM (Wimax) modulated signal with EVM of 2.94% at an average output power of 50 W and gain of 13.0 dB from simulating result. The design has good efficiency and linearity. All of these performances are satisfied with the OFDM systempsilas requirement of RF. This design may be applied for the OFDM systems compare with the standard of OFDM.