TY - GEN
T1 - Efficiency enhancement and linearity trade-offs for cascode vs. common-emitter SiGe power amplifiers in WiMAX polar transmitters
AU - Li, Yan
AU - Lopez, Jerry
AU - Lie, Donald Y.C.
AU - Chen, Kevin
AU - Wu, Stanley
AU - Yang, Tzu Yi
PY - 2010
Y1 - 2010
N2 - In this paper, a monolithic RF cascode SiGe power amplifier (PA) design capable of enhancing its power-added efficiency (PAE) is demonstrated. Four RF switches are adopted at the bases of the common-emitter transistors, which can be turned on/off in response to the desired output power. Simulations show that by utilizing device size variation, our cascode PA achieves higher gain and PAE compared to conventional fixed-size cascode PA in the low power region; in addition, it also provides more output power and higher average PAE than single-stage common-emitter PAs. We also studied and compared the linearity performance of our cascode PAs vs. single-stage common-emitter PAs in a RF polar TX using an envelope tracking (ET) technique. We found that even through self-biasing for the common-base device can improve the output distortion of cascode PAs, a single-stage common-emitter SiGe PA designed for comparison is still considerably more linear than cascode PAs. Therefore, more careful system linearization design will be critical when the cascode PAs are adopted in RF polar transmitters (TXs), especially for broadband wireless applications such as mobile WiMAX studied here.
AB - In this paper, a monolithic RF cascode SiGe power amplifier (PA) design capable of enhancing its power-added efficiency (PAE) is demonstrated. Four RF switches are adopted at the bases of the common-emitter transistors, which can be turned on/off in response to the desired output power. Simulations show that by utilizing device size variation, our cascode PA achieves higher gain and PAE compared to conventional fixed-size cascode PA in the low power region; in addition, it also provides more output power and higher average PAE than single-stage common-emitter PAs. We also studied and compared the linearity performance of our cascode PAs vs. single-stage common-emitter PAs in a RF polar TX using an envelope tracking (ET) technique. We found that even through self-biasing for the common-base device can improve the output distortion of cascode PAs, a single-stage common-emitter SiGe PA designed for comparison is still considerably more linear than cascode PAs. Therefore, more careful system linearization design will be critical when the cascode PAs are adopted in RF polar transmitters (TXs), especially for broadband wireless applications such as mobile WiMAX studied here.
UR - http://www.scopus.com/inward/record.url?scp=77955987725&partnerID=8YFLogxK
U2 - 10.1109/ISCAS.2010.5537979
DO - 10.1109/ISCAS.2010.5537979
M3 - Conference contribution
AN - SCOPUS:77955987725
SN - 9781424453085
T3 - ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems
SP - 1915
EP - 1918
BT - ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems
T2 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, ISCAS 2010
Y2 - 30 May 2010 through 2 June 2010
ER -