Anti-helicopter mine(AHM) based on the technology of passive acoustic detection and infrared detection and explosive forming pellet is an important weapon system to defend arming helicopter hedgehopping. Target’s direction and distance are detected by sound sensor array by reason of the directional sound propagation and high intensity noise emitted by a helicopter flying in air. The microphone in the sound sensor array detects the sound signal emitted by target, the direction and distance can be calculated by the time-delay among microphones. Because the target signals consist mainly of line spectrum, using narrow-band filter in system can improves SNR(Signal Noise Ratio) effectively. Target is moving, even if the frequency of target’s sound source is constant, the frequency change caused Doppler effect also isn’t ignored, the center frequency of narrow-band filter in anti-helicopter mine must be corresponding to a spectrum line of the target’s sound source. It is a problem faced by anti-helicopter mine with narrow band filter that tracing target’s frequency. After the change rate of the target’s frequency is analyzed, a method is introduced that three narrow-band filters with different center frequency are used in the same data channel and the center frequency is updated according to the parabolic interpolation of the peak values of three filters in a periods. Analysis results show that the method can perform the need of anti-helicopter.
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