Title :
A Low-Current Digitally Predistorted Direct-Conversion Transmitter With 25% Duty-Cycle Passive Mixer
Author :
Collados, Manel ; Hongli Zhang ; Tenbroek, Bernard ; Hsiang-Hui Chang
Author_Institution :
MTK Wireless Ltd., West Malling, UK
Abstract :
A low-current direct-conversion transmitter (TX) is obtained by combining an efficient single-balanced 25% duty-cycle passive mixer with a low-bias single-ended driver. The nonlinearity of such architecture is aggravated by strong harmonics at the mixer output folding down to the fundamental frequency due to driver nonlinearity. To address this, a baseband mathematical model of the passive mixer plus nonlinear driver is derived. Then, based on this model, a novel digital-predistortion approach is disclosed. Implemented in 40-nm CMOS, the modulator and driver combined consume 45 mW when delivering a +3-dBm Release 99 WCDMA signal with 0.9% error vector magnitude (EVM) and -59-dBc adjacent-channel leakage power ratio (ACLR). In long-term evolution (LTE) mode, the TX delivers +0-dBm 10-MHz LTE 16QAM with -53-dBc ACLR and 1.2% EVM.
Keywords :
CMOS integrated circuits; Long Term Evolution; code division multiple access; driver circuits; low-power electronics; mixers (circuits); nonlinear network analysis; power amplifiers; quadrature amplitude modulation; radio transmitters; 16QAM; CMOS integrated circuit; LTE; WCDMA signal; baseband mathematical model; digitally predistorted direct conversion transmitter; long term evolution; low bias single ended driver; low current transmitter; mixer output harmonics; nonlinear driver; passive mixer; power 45 mW; size 40 nm; Harmonic analysis; Mathematical model; Mixers; Modulation; Nonlinear distortion; Polynomials; Vectors; CMOS; WCDMA; digital; driver; harmonic; linearity; long-term evolution (LTE); mixer; modulator; nonlinear; passive; predistortion; transmitter (TX);
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
DOI :
10.1109/TMTT.2014.2309559
