1-bit Feedforward Distortion Compensation Technology for Bandpass Delta-Sigma Modulation

Takashi MAEHATA  Suguru KAMEDA  Noriharu SUEMATSU  

IEICE TRANSACTIONS on Communications   Vol.E99-B   No.5   pp.1087-1092
Publication Date: 2016/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.2015EBP3441
Type of Manuscript: PAPER
Category: Fundamental Theories for Communications
bandpass,  delta-sigma modulator,  feedforward compensation,  D/A converter,  

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This paper proposes 1-bit feedforward distortion compensation for digital radio frequency conversion (DRFC) with 1-bit bandpass delta-sigma modulation (BP-DSM). The 1-bit BP-DSM allows direct RF signal transmission from a digitally modulated signal. However, it has been previously reported that 1-bit digital pulse trains with non-ideal rectangle waveform cause spectrum regrowth. The proposed architecture adds a feedforward path with another 1-bit BP-DSM and so can cancel out the distortion components at any target carrier frequency. Both the main signal and the distortion compensation signal are 1-bit digital pulse trains and so no additional analog RF circuit is required for distortion compensation. Simulation results show that the proposed method holds the adjacent channel leakage ratio to 60dB for LTE signal transmission. A prototype of the proposed 1-bit DRFC with an additional 1-bit BP-DSM in the feedforward path shows an ACLR of 50dB, 4dB higher than that of the conventional 1-bit DRFC.