Sensitivity of spectrum analyzer

[abhijitrc]

How can we define the sensitivity of a spectrum analyzer ? is it same as that of normal receiver and can anybody write the equation.

 

[D.A.(Tony)Stewart]

Spectrum analyzers usually characterize this by specifying the displayed average noise level (DANL) in dBm, with the
smallest RBW setting. DANL is just another term for the noise floor of the instrument given a particular bandwidth. It
represents the best-case sensitivity of the spectrum analyzer, and is the ultimate limitation in making measurements on
small signals. An input signal below this noise level cannot be detected. Generally, sensitivity is on the order of -90
dBm to -145 dBm.The best SNR is with the lowest possible RF input attenuation.

Spectrum analyzer noise is specified in a specific RBW. The spectrum analyzer's lowest noise level (and slowest
sweeptime) is achieved with its narrowest RBW. changing the VBW does not improve sensitivity

 

[0dBc]

sensitivity of an SA is similar to sensitivity of a normal receiver: -174 + 10*LOG(RBW) + NF + SNR
here NF is the noise figure (in dB) of the spectrum analyzer at the given setting. Since SA is a general purpose receiver the SNR term is dropped and the rest is called DANL. As SunnySkyGuy said usually the DANL is given in the datasheets.