Agile Single- and Dual-Band All-Digital Transmitter Based on a Precompensated Tunable Delta–Sigma Modulator
; Cordeiro, R.
Barradas, F. M. B.
IEEE Transactions on Microwave Theory and Techniques Vol. 64, Nº 12, pp. 4720 - 4730, December, 2016.
ISSN (print): 0018-9480
Journal Impact Factor: 2,711 (in 2008)
Digital Object Identifier: 10.1109/TMTT.2016.2622696
In this paper a new architecture for designing
tunable, single- and dual-band Radio-Frequency (RF) fully digital
transmitters is proposed and validated. The proposed architecture
excels the state-of-the-art in terms of simplicity and
flexibility. While its short critical path leverages the use of
equivalent polyphase decomposition techniques to increase the
global system’s sampling frequency, the capability of changing
the system’s frequency response in real-time enables its use in
both single- or dual-band transmission scenarios. To mitigate a
crosstalk in the dual-band scenario, a pre-compensation technique
is also proposed. This novel concept has been successfully
validated in a Field-Programmable Gate Array (FPGA) based
transmitter. To validate both the proposed transmitter as well
as the pre-compensation mechanism, spectrum and Error-Vector
Magnitude (EVM) measurements were obtained for two scenarios
with a carrier frequency of 2.5 GHz: (i) single-band, using
QPSK, 16-Quadrature Amplitude Modulation (QAM) and 64-
QAM, with no Intermediate Frequency (IF), for different Symbol
Rate (SR) values (from 3.125 Msps up to 15.625 Msps); (ii) singleand
dual-band, using QPSK and 16-QAM, with a SR of 3.125
Msps, for different IF values (from 2 MHz up to 120 MHz).
All the experimental results present EVM values below 2.6%,
resulting in a well-defined constellation.