Title :
An envelope tracking power amplifier using an adaptive biased envelope amplifier for WCDMA handsets
Author :
Takahashi, Kiyohiko ; Yamanouchi, Shingo ; Hirayama, Tomohisa ; Kunihiro, Kazuaki
Author_Institution :
Device Platforms Res. Labs., NEC Corp., Kanagawa
fDate :
June 17 2008-April 17 2008
Abstract :
An envelope tracking power amplifier (ET-PA) using a self-oscillation pulse-width-modulation circuit with an adaptive bias technique is presented. In this technique, the supply voltage to the envelope amplifier is changed depending on the output power level. Since this approach enables the envelope amplifier to change the output power without degrading the signal resolution, the developed ET-PA shows a low adjacent channel leakage power ratio (ACPR) of less than -38 dBc in a wide output power range from 10 to 27 dBm. The ET-PA shows 45.4% overall efficiency at peak output power of 28 dBm. The average efficiency was 29%, which is 2.4 times higher than that of a class-AB PA. The noise power in the receive band (Rx noise) is -136 dBm/Hz at output power of 26 dBm at a frequency of 2.14 GHz.
Keywords :
UHF power amplifiers; circuit oscillations; code division multiple access; mobile handsets; pulse width modulation; WCDMA handsets; adaptive biased envelope amplifier; adjacent channel leakage power ratio; efficiency 29 percent; efficiency 45.4 percent; envelope tracking power amplifier; frequency 2.14 GHz; self-oscillation pulse-width-modulation circuit; Degradation; Frequency; Multiaccess communication; Power amplifiers; Power generation; Pulse amplifiers; Pulse circuits; Signal resolution; Telephone sets; Voltage; 0.18-μm CMOS; Envelope tracking; code division multiple access (CDMA); power amplifier; pulse width modulation (PWM);
Conference_Titel :
Radio Frequency Integrated Circuits Symposium, 2008. RFIC 2008. IEEE
Conference_Location :
Atlanta, GA
Print_ISBN :
978-1-4244-1808-4
Electronic_ISBN :
1529-2517
DOI :
10.1109/RFIC.2008.4561464
