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Direct-RF Delta-Sigma Transmitters

Broad adoption of wireless communication forces transceivers to operate in spectrally crowded environments with each mobile generation requiring wider instantaneous bandwidths. This crowded and rapidly changing wireless environment necessitates radios which are flexible with respect to carrier frequency and adaptable with respect to modulation scheme and bandwidth. Critical to these systems are high-performance DACs which facilitate RF synthesis directly from digital inputs.

To meet these demands, a time-interleaved 
DAC with reconfigurable ΔΣ modulation is proposed. By interleaving, the architecture cancels unwanted replica images which corrupt the output spectrum, enabling multi-Nyquist ΔΣ passbands which increases the low-noise bandwidth of the system. The proposed ΔΣ modulator utilizes a reconfigurable feedback filter to select among several passbands periodically distributed in frequency. Switching between these filter functions enables the design to adaptively generate low-noise signals directly at RF.

Students Involved: J. J. McCue