  Diamond quantum sensors are sensitive to weak microwave magnetic fields
resonant to the spin transitions. However the spectral resolution in such
protocols is limited ultimately by sensor lifetime. Here we demonstrate a
heterodyne detection method for microwaves (MW) leading to a lifetime
independent spectral resolution in the GHz range. We reference the MW-signal to
a local oscillator by generating the initial superposition state from a
coherent source. Experimentally we achieve a spectral resolution below $1\
\rm{Hz}$ for a $4\ \rm{GHz}$ signal far below the sensor lifetime limit of
kilohertz. Furthermore we show control over the interaction of the MW-field
with the two level system by applying dressing fields, pulsed Mollow absorption
and Floquet dynamics under strong longitudinal radio frequency drive. While
pulsed Mollow absorption leads to highest sensitivity, the Floquet dynamics
allows robust control independent from the systems resonance frequency. Our
work is important for future studies in sensing weak microwave signals in wide
frequency range with high spectral resolution.
