Fourier Series and Signal Power

Cuthbert Nyack
Assuming f(t) is a voltage applied across a 1ohm resistor then the average power in the signal f(t) is:-
The power can also be obtained from the coefficients of the Fourier Series:-
Eg. For a Square Wave with coefficients:-
The percent of the power in the fundamental is:-

The applet below shows how the power in the harmonics approaches the wave power as the number of terms summed is increased. Psq is the power in the harmonics for a square wave and Ptr is for a triangular wave. In each case, the power is normalised to the wave value.

When activated the following gif image show how the applet should appear.

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COPYRIGHT © 1996 Cuthbert Nyack.