Detection of helicopter signals using cyclostationarity

Experimental results on the study of helicopter acoustic signals with nonstationary additive noises using cyclostationarity are presented. It is shown that helicopter signals are closely related to first-order periodicity rather than to second- or higher order periodicity, and hence it is necessary to discuss the feasibility of detecting first-order periodicity using cyclostationarity. Working on real helicopter data, we then show that some advantages of using cyclostationarity for helicopter signal detection are improvement of (cyclic) frequency resolution and enhancement of the probability of detection. For helicopter signals with time-variant Doppler shift, a cyclic frequency smoothing method is proposed. This method does not have a counterpart in communication applications, and should be useful for acoustic signal processing