  We analyze performance of a resonance-type spin-torque microwave detector
(STMD) in the presence of noise and reveal two distinct regimes of STMD
operation. In the first (high-frequency) regime the minimum detectable
microwave power $P_{\rm min}$ is limited by the low-frequency Johnson-Nyquist
noise and the signal-to-noise ratio (SNR) of STMD is proportional to the input
microwave power $P_{\rm RF}$. In the second (low-frequency) regime $P_{\rm
min}$ is limited by the magnetic noise, and the SNR is proportional to
$\sqrt{P_{\rm RF}}$. The developed formalism can be used for the optimization
of the practical noise-handling parameters of a STMD.
