Spectrum Analyzer units of measure
Converting from dBm/Hz to V/√Hz
Written by Paul Cracknell
Updated at August 30th, 2024
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The Moku Spectrum Analyzer can display the spectrum amplitude in various units (dBm, Vrms, Vpp, and dBV). Additionally, you can select corresponding power spectral density (PSD) units (dBm/Hz, Vrms/√ Hz, Vpp/√Hz, and dBV/√ Hz). It is worth noting that the Resolution Bandwidth (RBW) setting only affects the measurement in PSD units.
Below is an example from demo mode, where the channel 1 peak is shown at -68.68 dBm/Hz.
This can be converted to Vrms/√Hz by relationship P [mW/Hz] = 10 (P [dBm/Hz] / 10)
So in this case, P = 1.355 x 10 -7 mW/Hz
Also, V= √( P x R) and that here 50 Ω is the conventional nominal impedance.
Thus the spectral peak in volts, allowing for conversion from mW to W, is
V = √( 50 x 1.35 x 10 -10)
V = 82.31 μV/√Hz
In this second screenshot of the Spectrum Analyzer in demo mode, the units have been switch to uV/√Hz.
