Title :
A hybrid envelope modulator using feedforward control for OFDM WLAN polar transmitter
Author :
Lee, Chih-Chang ; Chen, Chun-Jen ; Wu, Szu-Hsien
Author_Institution :
SoC Technol. Center, Ind. Technol. Res. Inst., Hsinchu, Taiwan
Abstract :
This paper presents a feedforward control for hybrid envelope modulator for applications in 802.11g OFDM WLAN polar transmitter. The feedforward control is constituted by hysteresis comparator and duplicate-linear amplifier that possess low power dissipation. For achieving high speed and high efficiency, the hybrid envelope modulator combines with a linear amplifier and a switch amplifier. Operational transconductance amplifier (OTA) and class-AB output stage are designed for linear amplifier as well as the buck converter is designed for switch amplifier. The chip has been fabricated in 0.35 mum SiGe process and occupies an area of 2 mm2 including I/O pads. The die is packaged in LQFP and measurement results show that the output voltage range is from 0 to 3 V under 3.8 V power supply and drives a 5 Omega load up to 1.8 W of maximum output power with 95% of maximum efficiency.
Keywords :
Ge-Si alloys; OFDM modulation; feedforward; modulators; radio transmitters; telecommunication control; wireless LAN; IEEE 802.11g; OFDM WLAN polar transmitter; SiGe; buck converter; duplicate-linear amplifier; efficiency 95 percent; feedforward control; hybrid envelope modulator; hysteresis comparator; operational transconductance amplifier; power 1.8 W; size 0.35 micron; voltage 0 V to 3 V; voltage 3.8 V; Buck converters; Hysteresis; OFDM modulation; Operational amplifiers; Power dissipation; Silicon germanium; Switches; Transconductance; Transmitters; Wireless LAN;
Conference_Titel :
Radio Frequency Integrated Circuits Symposium, 2009. RFIC 2009. IEEE
Conference_Location :
Boston, MA
Print_ISBN :
978-1-4244-3377-3
Electronic_ISBN :
1529-2517
DOI :
10.1109/RFIC.2009.5135508
