SEA-BOTTOM GUARD DEVICE Russian patent published in 2008 - IPC F42B22/06 

FIELD: sea material, applicable for protection of water areas closed for navigation.

SUBSTANCE: the device has an alert channel responsive to the combined action of the own fields of the transgressor ship, for example, the hydroacoustic, electromagnetic, hydrodynamic fields, and an actuating mechanism. An active hydroacoustive channel is additionally connected between the alert channel and the actuating mechanism. The active channel is located in a non-magnetic float. The float is coupled to the body of the sea guard device lying in the bottom through a short non-magnetic cable-cord. The active channel includes directive hydroacoustic antennas uniformly oriented to all the sectors of the hemisphere: bottom-surface, sounding signal transmitter and echo-signal receivers, whose number equals the number of antennas. The output of the alert channels is connected to the transmitter start input. The transmitter output is parallel-connected to all the antennas. The input of each receiver is connected to one of the antennas. The receiver channel has series-connected time selector for reception of the echo-signal in the operating zone of action of the guard device, amplifier, frequency filter matched with the Doppler shift of the frequency of the echo signal from the transgressor ship, echo-signal detector and a comparator. One comparison input of the comparator is connected to the detector of the receiver operating from the antenna of one of the sectors. The other comparison input of the comparator is connected to the detectors of the receivers operating from the antennas of the sector mentioned antenna via the matrix forming the arithmetic mean. The outputs of all the comparators via an OR-gate are connected to the input of the actuating mechanism start.

EFFECT: enhanced noise immunity.

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