Fourier-Domain DAC-Based Wireless Transmitter With Up To 2-GHz Modulation Bandwidth

Abstract

This article presents a fully integrated Fourier-domain digital-to-analog converter-based transmitter (Tx). The proposed topology generates a coherent bandwidth (BW) of up to 2 GHz by exploiting the relationship between the discrete and the continuous-time Fourier transform. Thus, the digital-to-analog converter (DAC) sampling rate and the entire digital signal processing (DSP) speed are reduced by up to two orders of magnitude compared to conventional Txs. Moreover, the proposed technique provides intrinsic spectral shaping increasing the spectral efficiency of the output signal. Thus, no complex and high-speed signal processing in terms of oversampling and filtering is required to provide spectral shaping in order to attenuate the out-of-band emissions. The proposed concept is experimentally demonstrated by a fully integrated Tx prototype, including the DSP in 65-nm CMOS technology. It generates a single-carrier signal with a modulation BW of up to 2 GHz and a modulation order of up to 16QAM in the sub-6-GHz frequency range. The occupied chip area is 1.34 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The best measured error vector magnitude (EVM) values with equalization are 13.6% and 17.7% for a 1- and 2-GHz QPSK signal, respectively, whereas for a 1-GHz-wide 16QAM signal, an EVM of 12.4% is measured. Thus, the maximum demonstrated data rate is 4 Gb/s.