  Developing frequency combs spectral technologies has potential applications
and prospects in the wide fields of cosmology, meteorology, and microwave
measurement. Here, we demonstrate a Rydberg microwave frequency comb
spectrometer via multiple-microwave field dressing, providing precise microwave
measurement. The Rydberg microwave frequency comb spectrum provides a real-time
and absolute frequency measurement with a range of 125 MHz and gives the
relative phase of a single-frequency microwave signal. The reported experiment
helps real-time sensing of an unknown microwave signal in a wide range using
Rydberg atoms, which are vital for Rydberg-atom-based microwave metrology.
