Spectrum Analyzer Noise Floor Calculator

This tool calculates the Noise floor of a spectrum analyzer. The noise floor represents the weakest possible signal that can be detected by the instrument.

Calculator

Enter

  • Displayed Average Noise Level (DANL)
  • Resolution Bandwidth
  • Transducer Factor (LISN)
  • Correction Factor

	

			

		

						

				

				

                

			

			
						

		

		











Formula





Spectrum Analyzer Noise Floor = DANL + 10*Log10(RBW) + Correction Factor + Transducer Factor 





Correction and Transducer factors are used in EMC testing and this is also called the System Noise Floor.





Example Calculation





For a DANL of -151 dBm/Hz and RBW = 1 MHz, Transducer Factor = 3 dB and Correction Factor = 3 dB, the noise floor of the spectrum analyzer is -85 dBm. The tool also provides the Watt equivalent or 3.16*10-12 W.





The picture below shows the variation of noise level with bandwidth










Practical Note





The lower the noise floor of the spectrum analyzer, the better it is at detecting weaker signals and consequently the more expensive it is.





A good spectrum analyzer will have a noise floor of -160 dBm/Hz or better at lower frequencies.





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