FM Bandwidth Calculator

This tool calculates the bandwidth of a Frequency Modulation (FM) signal. It also finds the modulation index. 


	

			

		

						

				

				

                

			

			
						

		

		






Formula





According to Carson’s rule states approximately 98% of the power of a frequency-modulated signal lies within a bandwidth given by the formula:





BT = 2*(Δf + fm)





where





    

  • Δf is the peak deviation of the instantaneous frequency from the carrier center frequency
    • 




  • fm is the highest frequency in the modulating signal
    • 






 the modulation index β is given by Δf/fm 





Example Calculation





A 5 kHz peak deviation of a 10 kHz audio signal results in a modulation index of 0.50 and a FM bandwidth of 30 kHz.





FM Calculators





These two calculators provide insight into the performance of FM transmitters and receivers









References





[1]  Carson’s Rule on Wikipedia





Related Calculators