that detects the impact signature processes it and calculates the time of arrival the system comprises a polyphase filter bank boxcar filter a detection analyzer for detecting an impact and time tagging software for calculating the time of impact the system splits the received hydrophone signal into evenly spaced energy bands processes each band individually and then recombines the data to provide a precise time of detection application_number US 71383707 A description fig3 shows a block diagram of a first embodiment of a polyphase detection system 46 according to the current invention the polyphase detector 46 registers several of the detection bands and thereby eliminates many false alarms a polyphase detector 46 can be designed by selecting a collection of n center frequencies distributed across the nyquist band 0 f s hz where f s is the sampling frequency for a signal for the input sample sequence the collection of n center frequencies u03c9 0 u03c9 1 u03c9 k u03c9 n 1 is given by the available number of channels and the sampling frequency of the system each single band detector frequency is given by the single band detector is processed by multiplying the input signal x n by this gives a signal that translates the spectrum of interest to the origin this also provides the power about that center frequency by squaring the signal this reduced bandwidth signal can be provided to a lowpass filter h n the lowpass filter bandwidth is selected as b u2266.