  Rydberg quantum sensors are sensitive to radio-frequency fields across an
ultra-wide frequency range spanning megahertz to terahertz electromagnetic
waves resonant with Rydberg atom dipole transitions. Here we demonstrate an
atomic millimeter-wave heterodyne receiver employing continuous-wave lasers
stabilized to an optical frequency comb. We characterize the atomic receiver in
the W-band at signal frequency of $f$=95.992512~GHz, and demonstrate a
sensitivity of 7.9$\mu$V/m/$\sqrt{Hz}$ and a linear dynamic range of 70dB. We
develop frequency selectivity metrics for atomic receivers and demonstrate
their use in our millimeter-wave receiver, including signal rejection levels at
signal frequency offsets $\Delta f/f$ = 10$^{-4}$, 10$^{-5}$ and 10$^{-6}$,
3-dB, 6-dB, 9-dB and 12-dB bandwidths, filter roll-off, and shape factor
analysis. Our work represents an important advance towards future studies and
applications of atomic receiver science and technology and in weak
millimeter-wave and high-frequency signal detection.
