85-to-127 GHz CMOS Transmitter for Rotational Spectroscopy

Abstract

A transmitter for rotational spectroscopy using a fractional-N PLL (FNPLL) that generates frequency shift keyed signals from 85 to 127 GHz (39% tuning range) with a fine frequency step of similar to 570 Hz and settling time of similar to 10 mu S is demonstrated. Implemented in 65-nm CMOS, the FNPLL delivers greater than 5 mu W of output power, and achieves measured phase noise of less than -70 dBc/Hz in-band and less than -102 dBc/Hz at 10-MHz offset over the output frequency range while consuming 80 mW. The transmitter output is radiated using a bond-wire antenna and successfully utilized in a spectrometer for detection of gas molecules.