A 23dBm fully digital transmitter using ΣΔ and pulse-width modulation for LTE and WLAN applications in 45nm CMOS

This paper presents a 23 dBm fully digital transmitter designed in a standard 45 nm CMOS process. The digital transmitter replaces the entire analog/RF signal chain in a traditional transmitter architecture. It utilizes ΣΔ modulation and pulse-width modulation to turn high resolution baseband I and Q signals into switching signals, thereby allowing efficient Class-D PA stages to be used. In addition, cascaded ΣΔ stages and switched-capacitor combining are incorporated into the architecture to reduced out-of-band quantization noise while maintaining good efficiency. The proposed transmitter achieves peak output power of 23 dBm with 47% power added efficiency (PAE). For a OFDM signal with 8.2 dB peak-to-average power ratio (PAR), the PAE is 23%. The linearity of the digital transmitter meets WiFi spectral mask without any digital predistortion.

[1]  Patrick Reynaert,et al.  Transformer-Based Uneven Doherty Power Amplifier in 90 nm CMOS for WLAN Applications , 2012, IEEE Journal of Solid-State Circuits.

[2]  Marian Verhelst,et al.  A 20dBm 2.4GHz digital outphasing transmitter for WLAN application in 32nm CMOS , 2012, 2012 IEEE International Solid-State Circuits Conference.

[3]  W. Marsden.  I and J , 2012 .

[4]  Shoji Otaka,et al.  A 1.8GHz linear CMOS power amplifier with supply-path switching scheme for WCDMA/LTE applications , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.

[5]  Jeffrey S. Walling,et al.  A switched-capacitor power amplifier for EER/polar transmitters , 2011, 2011 IEEE International Solid-State Circuits Conference.

[6]  Baher Haroun,et al.  A 110dB SNR and 0.5mW current-steering audio DAC implemented in 45nm CMOS , 2010, 2010 IEEE International Solid-State Circuits Conference - (ISSCC).

[7]  SungWon Chung,et al.  A 2.5-GHz asymmetric multilevel outphasing power amplifier in 65-nm CMOS , 2011, 2011 IEEE Topical Conference on Power Amplifiers for Wireless and Radio Applications.

[8]  Ali M. Niknejad,et al.  A digitally modulated 2.4GHz WLAN transmitter with integrated phase path and dynamic load modulation in 65nm CMOS , 2013, 2013 IEEE International Solid-State Circuits Conference Digest of Technical Papers.