25.2 A 210-to-305GHz CMOS receiver for rotational spectroscopy

Electromagnetic waves in the millimeter- and sub-millimeter-wave frequency ranges are used in fast-scan rotational spectroscopy to detect gas molecules and measure their concentrations [1]. This technique can be used for indoor air quality monitoring, detection of toxic gas leaks, breath analyses for monitoring bodily conditions and many others. This paper reports a 210-to-305GHz receiver (RX) front-end for a rotational spectrometer that achieves SSB noise figure (NF) of 13.9 to 19dB by incorporating an on-chip antenna with a reflector formed using a phase-compensated artificial magnetic conductor (PC-AMC) instead a metal reflector to improve the bandwidth of the antenna, a single balanced subharmonic mixer using a pair of floating-body NMOS anti-parallel diode pairs (FB-APDPs), a hybrid-based broadband port-isolation structure, and a 20-GHz low-noise intermediate frequency (IF) amplifier (Fig. 25.2.1). The front-end is fabricated in a 65nm CMOS process that supports isolated p-wells and 10 copper layers with a ~3μm thick 10
^th
metal layer.