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 (ΔΣ) 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 ΔΣ modulator has been previously proposed [1], [2]. 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 ΔΣ 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 ΔΣ modulator synthesis.