CMOS 300-GHz 64-QAM transmitter

A QAM-capable 300-GHz transmitter operating above the transistor ƒmax, covering a 30-GHz bandwidth with multiple channels was recently reported. A key enabling component was a tripler-based up-conversion mixer called the “cubic mixer.” This paper theoretically and experimentally studies the S/N characteristics of such a mixer and elucidates the condition for realizing high single-channel data-rate. 30 Gb/s with 32QAM and 21 Gb/s with 64QAM are achieved under optimal conditions, which are faster than the previously reported per-channel data-rate of 17.5 Gb/s.