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In this paper, an 8-bit envelope modulator as part of a digital polar transmitter for Bluetooth and WLAN is demonstrated. The modulator performs digital-to-analog conversion, up-mixing and power amplification, allowing for an area-efficient, fully-integrated transmitter architecture. The circuit delivers 24.8 dBm peak-power and 16.7 dBm WLAN OFDM power with a mean EVM of 2.7% at 2 GHz. The measured peak-power drain efficiency is 51% while the efficiency for OFDM is 24%. In Bluetooth EDR mode a 19.7 dBm signal with 5%-rms, 13%-peak EVM, and 26% drain efficiency has been measured. The circuit is fabricated in CMOS 65 nm with 50 Aring thick-oxide devices and 2.5 V power supply.
Date of Conference: 21-24 Sept. 2008