As a wireless handset deals with multiple application standards concurrently, RF transmitters and power amplifiers are required to be more power efficient and reconfigurable. In this paper, we review the recent advances in the design of the power amplifiers and transmitters. Then, the systematic design approaches to improve the performance with the digital baseband signal processing are introduced for the next generation mobile handset.
The input power drive of Doherty power amplifier (PA) is analyzed and a proper input dividing technique without a coupler is introduced. The efficiency and linearity are enhanced by the uneven power drive and proposed output matching circuits. The PA circuit is realized using a 2-μm InGaP/GaAs HBT process and combined using merged lumped-components for Doherty operation. For wireless broadband (WiBro) application, which has 9.54 dB crest factor and 8.75 MHz bandwidth, the PA has EVM of 3% and PAE of 40.2% at an output power of 26 dBm. This data represents that the PA has an excellent efficiency and linearity performance for handset applications, while eliminating the burden of a coupler.
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