Can spectral density be a complex quantity?

1. Can power spectrum be complex?
2. What are the units of spectral density?
3. How is spectral density measured?
4. Is Power Spectral Density always real?

Can power spectrum be complex?

The discrete Fourier transform (DFT) or fast Fourier transform (FFT) of a real signal is a complex number, having a real and an imaginary part.

What are the units of spectral density?

Power spectral density is commonly expressed in watts per hertz (W/Hz).

How is spectral density measured?

Answer. PSD is typically measured in units of V_rms² /Hz or V_rms/rt Hz , where "rt Hz" means "square root Hertz". Alternatively, PSD can be expressed in units of dBm/Hz. On a spectrum analyzer such as the PSA, ESA, 856XE/EC or 859XE, power spectral density can be measured with the noise marker.

Is Power Spectral Density always real?

Signal processing

The PSDs and (also called autospectral densities) are even, real-valued, and positive functions. The cross-spectral density is in general a complex-valued function.