Hi,

I am interested in the exact signal power of a time signal. Hence I set up a QPSK source with a timed sink (50 Ohm) and a spectrum analyser in parallel at the output.

First I calculate the signal power in the time domain (which should lead to the exact value) from the rms value of the signal (T_V). ->

Ueff_V = sqrt(sum(mag(T_V)**2)/numberofsimpoints)

P_W = Ueff_V**2/50

P_dBm = 10*log10(P_V/1e-3)

This leads to a value which is 2.8 dB above the nominal power level of the QPSK modulator of 0 dBm. Using spec_power() on the output of the SpecAnalyser compontent leads as well to a value of 0 dBm.

What is wrong here? Any idea? Please let me know.

Thank you Wolfram???

I am interested in the exact signal power of a time signal. Hence I set up a QPSK source with a timed sink (50 Ohm) and a spectrum analyser in parallel at the output.

First I calculate the signal power in the time domain (which should lead to the exact value) from the rms value of the signal (T_V). ->

Ueff_V = sqrt(sum(mag(T_V)**2)/numberofsimpoints)

P_W = Ueff_V**2/50

P_dBm = 10*log10(P_V/1e-3)

This leads to a value which is 2.8 dB above the nominal power level of the QPSK modulator of 0 dBm. Using spec_power() on the output of the SpecAnalyser compontent leads as well to a value of 0 dBm.

What is wrong here? Any idea? Please let me know.

Thank you Wolfram???

Depending on whether your signal is timed BB or RF, there is a factor 2 difference which may have caused this discrepency. Take a look at TkPower subnetwork and how the parameter SignalType impacts the power calculation