  Classical sensors for spectrum analysis are widely used but lack micro- or
nanoscale spatial resolution. On the other hand, quantum sensors, capable of
working with nanoscale precision, do not provide precise frequency resolution
over a wide range of frequencies. Using a single spin in diamond, we present a
measurement protocol for quantum probes which enables full signal
reconstruction on a nanoscale spatial resolution up to potentially 100\,GHz. We
achieve $58\,\mathrm{nT/\sqrt{Hz}}$ amplitude and
$0.095\,\mathrm{rad/\sqrt{Hz}}$ phase sensitivity and a relative frequency
uncertainty of $10^{-12}$ for a $1.51\,\mathrm{GHz}$ signal within
$10\,\mathrm{s}$ of integration. This technique opens the way to quantum
spectrum analysis methods with potential applications in electron spin
detection and nanocircuitry in quantum technologies.
