Title :
Doherty amplifier with DSP control to improve performance in CDMA operation
Author :
Yu Zhao ; Iwamoto, M. ; Larson, L.E. ; Asbeck, P.M.
Author_Institution :
Dept. of Electr. & Comput. Eng., Univ. of California, La Jolla, CA, USA
Abstract :
A power amplifier for CDMA applications which consists of a Doherty amplifier and a digital signal processing (DSP) controller is presented. DSP is used to dynamically adjust the gate bias of the auxiliary (peaking) amplifier at the rate of the signal envelope to obtain gain flatness (i.e. AM-AM distortion correction). Furthermore, DSP is used as a digital predistortor to improve the overall linearity by adjusting the phase at baseband (i.e. AM-PM distortion correction). The 840 MHz Doherty amplifier is realized with two commercially available MESFETs in a hybrid circuit, and the DSP is implemented externally with a board controlled by a personal computer. It is shown that by utilizing these DSP techniques, the overall linearity and efficiency characteristics of the Doherty amplifier can be significantly improved.
Keywords :
MESFET circuits; UHF power amplifiers; code division multiple access; digital signal processing chips; 840 MHz; AM-AM distortion; AM-PM distortion; CDMA operation; DSP control; Doherty amplifier; MESFET hybrid circuit; digital predistortion; efficiency; gain flatness; linearity; personal computer; power amplifier; Baseband; Circuits; Digital signal processing; Linearity; MESFETs; Microcomputers; Multiaccess communication; Operational amplifiers; Power amplifiers; Process control;
Conference_Titel :
Microwave Symposium Digest, 2003 IEEE MTT-S International
Conference_Location :
Philadelphia, PA, USA
Print_ISBN :
0-7803-7695-1
DOI :
10.1109/MWSYM.2003.1212465
