The Dynamic Analysis of the Averaging Type FM Discriminator

The dynamic response of an averaging type FM discriminator to a general FM input is analysed on the assumption that the zero crossing of the input signal initiates impulses which are applied to a low pass filter. The boundaries between which the output voltage of that filter is varying are evaluated. The faithful decoding may start after an initial settling-down period which is often found to be short compared with the actual period of the measurement. In order to show the practical use of the result obtained, two examples are given which deal with a linear and a parabolic change of the frequency with time.