Calculate power spectral density, total power, or bandwidth, plus kTB thermal noise and RMS voltage or current noise from density and bandwidth.

Power Spectral Density Formula

The following formula is used to calculate the Power Spectral Density. 

PSD = P / BW
  • Where PSD is the band-average Power Spectral Density (W/Hz)
  • P is the total signal power (W) 
  • BW is the total bandwidth (Hz) 

To calculate the band-average spectral density, divide signal power in watts by bandwidth in hertz. A flat spectrum has this density throughout the band.

How to Calculate Power Spectral Density?

The following example problems outline how to calculate Power Spectral Density.

Example Problem #1:

  1. First, determine the total signal power.
    1. The total signal power is given as 40 W.
  2. Next, determine the total bandwidth.
    1. The total bandwidth is provided as 10 Hz.
  3. Finally, calculate the Power Spectral Density using the equation above: 

PSD = P / BW

The values given above are inserted into the equation below:

PSD = 40 W / 10 Hz = 4 W/Hz

Example Problem #2: 

For this problem, the variables needed are provided below:

total signal power  = 75 W

total bandwidth  = 20 Hz

This example problem is a test of your knowledge on the subject. Use the calculator above to check your answer. 

PSD = P / BW = ?