The interception of spread spectrum waveforms via the amplitude distribution function

Within the context of unfriendly detection and interception of secure communications, an innovative concept called the amplitude distribution function (ADF) is used to construct a detector that is an enhancement to the radiometer. The ADF is developed and shown to be roughly the average probability distribution of a random process. The significance of ADF is that under most spreading modulations, the ADF is invariant. Modulation invariance suggests that a detector built around the ADF concept can be robust and general purpose. To indirectly estimate the ADF from observations, the amplitude moment statistic (AMS) is defined and used for detecting a sinusoid in stationary Gaussian noise. Detection performance is then analyzed, compared with that of a radiometer, and shown superior for small time-bandwidth products