Linearity and Efficiency Strategies for Next-Generation Wireless Communications
Third-generation cellular wireless services are gradually being deployed on a worldwide basis, and wider bandwidth data-oriented OFDM-based standards such as WiMax and 802.11b/g/n are also becoming popular. These new services—and the 4G systems that will follow—require wider RF bandwidths and more exotic modulation schemes than those of previous physical-layer approaches. These new standards are also required to share the spectrum with existing 2G systems such as GSM and CDMA and their legacy frequencies. As a result, multi-mode/multi-band mobile terminals are now standard, and the need for these functions will increase over time. As we will see in this chapter, this evolution of wireless technology places an enormous burden on power amplifier technology. We summarize the key technical challenges presented by this evolution and present technical strategies to maintain high-power amplifier performance.
12.2 POWER AMPLIFIER FUNCTION
In the line-up of the modern wireless communications transmitter system, the linear power amplifier is the final interface between the baseband signal processing/RF up-converter and the antenna. When viewed in this light, the power amplifier function appears to be a simple amplification of the input signal and delivery of the resulting ...