I am looking for the formula to convert the power level of an OFDM RF signal to an absolute power level. For example if I have my typical rectangular RF spectrum and the bandwidth of the signal is 10MHz, if my signal power needs to be 23dBm, what power do I need to measure on the plateau of the rectangular OFDM signal?

For example I saw a measurement function in a spectrum analyser where you could bring up markers and it would give an RF power level measured across that bandwidth, I remember seeing the waveform peak at about -20dBm but integrated across the bandwidth the power level came out to be around 1dBm.

I would like to know the formula. if I know the bandwidth of my OFDM signal and know what power level i need to reach, what level should I measure at the peak of my RF signal?

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    – Andy aka
    Commented Aug 4, 2020 at 9:51

1 Answer 1


Assuming the power spectral density (watts per Hz) are constant then take the overall power of 23 dBm and convert it to real power: -

$$\text{real power} = 10^{\frac{23}{10}} = 200 \text{ mW} $$

Next divide that by bandwidth (10 MHz) to get power per Hz: -

$$ 20 \text{ nano watts per Hz}$$ $$ = -77 \text{ dBW per Hz}$$ $$ = -47 \text{ dBm per Hz}$$


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