Anti-submarine warfare mine

Claim 2

An anti-submarine warfare (ASW) mine comprising; a) a housing including a torpedo compartment and a head compartment; b) sensor support electronics operatively mounted in the head compartment; and c) a plurality of magnetic sensor means exteriorly attached to the housing and operatively connected to the support electronics for sensing the Earth's magnetic field, whereby the sensor support electronics controls the operation of the magnetic sensor means, detects variations in the Earth's magnetic field resulting from the presence of ferromagnetic bodies and produces mine influence signals.

Claim 3

An ASW mine according to claim 1 further including port cover removing means mounted in said housing and wherein the torpedo compartment includes a port having a removable cover, said port cover removing means operatively connected to the port cover for removing the port cover and flooding the torpedo compartment.

Claim 4

An ASW mine according to claim 1 further including a spring between the torpedo compartment and head compartment for selectively separating the head compartment from the torpedo compartment.

Claim 5

An ASW mine according to claim 1 wherein the plurality of magnetic sensor means includes a plurality of sensor pods, a corresponding plurality of He³ magnetic sensors mounted in each pod, a corresponding plurality of rods interconnecting the pods and head compartment, and a plurality of electrical cables interconnecting the plurality of sensors to the sensor support electronics.

Claim 6

An ASW mine according to claim 4 wherein each He³ sensor includes a cell containing He³ atoms, some of which are temporarily excited to a metastable state, a He⁴ lamp, lens and polarizer forming an optical path to the cell for producing collimated, circular polarized electromagnetic radiation energy for magnetizing the He³ atoms in the cell in a direction parallel to the ambient magnetic field, a Helmholtz coil in operative association with the cell or establishing an oscillatory magnetic field normal to that of the ambient magnetic field, and pickup coils operative during free precession of the cell for generating a.c. induced therein by the magnetic field associated with the rotation of the cell magnetization.

Claim 7

An ASW mine according to claim 5 wherein the sensor support electronics includes a phase locked loop and support electronics means for providing excitation, ignition and rotation signals, an exciter oscillator and an ignition oscillator for each of the plurality of He³ sensors, the ignition oscillator operatively connected to the phase locked loop and support electronics means for receiving the excitation signal and to the He³ cell and He⁴ lamp for exciting the cell and preparing the lamp for ignition, and the exciter oscillator operatively connected to the phase locked loop and support means for receiving the ignition signal and to the lamp for ignition, a phase locked loop frequency discriminator of the phase locked loop and support electronics means operatively connected to the Helmholtz coil of the sensor for providing the rotation signals to the coil for establishing the oscillating magnetic field normal to the ambient magnetic field, and preamplifiers operatively connected to the pickup coils for amplifying the magnetic field associated with the precession of the cell atoms for the phase locked loop and support electronics means, a fluxgate magnetometer for determining the motion attitude of the housing, and a signal processor operatively connected to the fluxgate magnetometer and phase locked loop of the phase locked loop and support electronics means or detecting the presence of ferromagnetic bodies and generating mine operating signals.

Claim 8

An ASW mine according to claim 6 wherein the phase locked loop and support electronics means includes a plurality of digital phase locked loop circuits corresponding to the plurality of magnetic sensors, said phase locked loop circuits producing digital signals corresponding to the magnetometer signal frequencies, a difference circuit operatively connected to the outputs of the phase locked loops and outputting the difference as a digital signal for the signal processor.

Claim 9

An ASW mine according to claim 7 wherein each digital phase locked loop includes a bandpass filter operatively connected to a sensor for removing noise signals, a multiplying digital to analog (D/A) converter operatively connected to the bandpass filter and digital VCO for phase detection, an anti-aliasing filter operatively connected to the multiplying D/A converter, an analog to digital (A/D) converter operatively connected to the anti-aliasing filter, a digital loop filter operatively connected to the A/D converter for integrating the signals with phase lead correction and determining the performance characteristics of the phase locked loop, and said digital VCO comprising an adder operatively connected to the digital filter, a holding register operatively connected to the adder and a read only memory (ROM) operatively connected to the holding register, said adder and holding register coacting to form an automatically rezeroing ramp generator with instantaneous slop controlled by the adder for producing a digital word representative of the phase of the digital VCO and the ROM for performing the cosine phase function for the multiplying D/A converter to complete the phase locked loop.

Claim 10

An ASW mine comprising a mine housing, a gradiometer operatively connected to the mine housing for generating magnetometer frequencies , a difference means operatively connected to the gradiometer for producing a difference signal representative of the frequency difference between the magnetometer frequencies of the gradiometer, and a signal processor operatively connected to the difference means for detecting the presence of a ferromagnetic body and generating a trigger to a mine torpedo.

Claim 11

An ASW mine comprising a mine housing, a gradiometer operatively connected to the mine housing for generating magnetometer frequencies , a difference means operatively connected to the gradiometer for producing a difference signal representative of the frequency difference between the magnetometer frequencies of the gradiometer, and a signal processor operatively connected to the difference means for detecting the presence of a ferromagnetic body and generating a trigger to a mine torpedo.

Claim 12

An ASW mine according to claim 9 wherein the gradiometer includes two sensors and a frequency discriminator.

Claim 13

An ASW mine according to claim 10 wherein the frequency discriminator is a digital phase locked loop.