A 19 dBm, 15 Gbaud, 9 bit SOI CMOS Power-DAC Cell for High-Order QAM W-Band Transmitters Stefan Shopov, Student Member , IEEE , Andreea Balteanu , Student Member , IEEE ,a n d Sorin P . V oinigescu, Senior Member , IEEE

Abstract

A mm-wave I-Q power-DAC is reported at -band. The circuit, which is fabricated in a 45 nm SOI CMOS technology, employs a series-stacked Gilbe rt-cell output stage with gate finger geometry segmentation to directly modulate a 85–95 GHz carrier. The Gilbert-cell provides phase inversion and 7 bits for ASK en- velope modulation, each of which can be switched at speeds up to 15 Gb/s. A ninth bit turns the entire DAC cell on and off at 15 Gb/s, as needed to create an arbitrary 15 Gbaud QAM con- stellation in a symmetrical 4×4 I–Q power-DAC transmitter array, with free-space power combining and antenna-level segmentation. The measured output power and PAE of the I or Q DAC cells are 19 dBm and 8.9%, respectively. Three effective bits of amplitude resolution and one phase bit are estimated from the small-signal S-parameter measurements in th e 80–95 GHz range. The envelope amplitude resolution reduces to on ly two effective bits under satu- rated output power operation. The OOK bit provides over 45 dB of measured attenuation and dynamic range, relative to the peak output power.