Reconfigurable digital Delta-Sigma Modulator Synthesis for digital wireless transmitters

Digital generation of radio-frequency signals is a key concept of software defined radios. One of the main difficulties for multi-standard transmitter design based on delta-sigma (DeltaSigma) modulators is to respect the different specifications in terms of out-of-band spurious emission. Focusing on the TX path of a UMTS/DCS1800 phone, a 3^rd order DeltaSigma modulator has been previously proposed by A. Frappe et al. (2006). But, the performances did not match both standards specifications. Hence, in this paper, we present a new method for the synthesis of a 5^th order DeltaSigma which allows, in the TX path, to effectively cancel out-of-band noise in agreement with specifications. Moreover, this approach eases the reconfiguration of the modulator, and on the other hand, it is a powerful tool for all order DeltaSigma modulator synthesis.