What's the most commonly used method in PA design ?

What's the most commonly used method in PA design for wireless communications such as WCDMA to enhance effciency and improve linearity?

Load pull and source pull. To improve the linearity, feedforward and preistortion are good techniques. To get more effeciency, Dorthy technique is popular. There are two books from Steven Clipp for both topics.

Polar Modulation

http://www.wsdmag.com/Articles/Artic...479/11479.html
http://commsdesign.com/printableArti...cleID=16503414

Which two books?where to download ?

thanks.

hxxp://file.21ic.com.cn/RFDesign/RF%20Power%20Amplifiers%20for%20Wireless%20Communi cations/