Atmospheric-Noise FSK Error Probabilities for an Envelope-Detection Receiver

A useful expression for FSK error probability with atmospheric noise interference, equal to one half the probability that the noise envelope exceeds the signal envelope, previously derived for a bandpass-filter discriminator FSK receiver applies as well to a matched-filter envelope-detection receiver. This error probability for Gaussian noise interference is equivalent to a more common expression defined in terms of signal energy and noise power density.